X-Git-Url: https://git.mxchange.org/?a=blobdiff_plain;f=src%2FCockpit%2Fpanel_io.cxx;h=0e395a31c08a2cf29a49739f81dd16eaf15ad733;hb=29275ce1ecf9c4ea302aacca8c5ae5d4d3319a17;hp=1175b0d7129f10937656babc6cba2408de4a1c21;hpb=a2cd367ab5061c62c1b6c2a0fd14b216956724af;p=flightgear.git

diff --git a/src/Cockpit/panel_io.cxx b/src/Cockpit/panel_io.cxx
index 1175b0d71..0e395a31c 100644
--- a/src/Cockpit/panel_io.cxx
+++ b/src/Cockpit/panel_io.cxx
@@ -27,68 +27,262 @@
 #endif
 
 #include <simgear/compiler.h>
+
+#include <simgear/misc/fgpath.hxx>
 #include <simgear/debug/logstream.hxx>
 #include <simgear/misc/props.hxx>
 
-#include <iostream>
-#include <string>
+#include STL_IOSTREAM
+#include STL_FSTREAM
+#include STL_STRING
+
+#include <Main/globals.hxx>
+#include <Main/fg_props.hxx>
 
 #include "panel.hxx"
+#include "steam.hxx"
+#include "panel_io.hxx"
+
+#if !defined (FG_HAVE_NATIVE_SGI_COMPILERS)
+FG_USING_STD(istream);
+FG_USING_STD(ifstream);
+#endif
+FG_USING_STD(string);
+
+
+
+////////////////////////////////////////////////////////////////////////
+// Default panel, instrument, and layer for when things go wrong...
+////////////////////////////////////////////////////////////////////////
+
+static FGCroppedTexture defaultTexture("Textures/default.rgb");
+
+
+/**
+ * Default layer: the default texture.
+ */
+class DefaultLayer : public FGTexturedLayer
+{
+public:
+  DefaultLayer () : FGTexturedLayer(defaultTexture)
+  {
+  }
+  
+};
+
+/**
+ * Default instrument: a single default layer.
+ */
+class DefaultInstrument : public FGLayeredInstrument
+{
+public:
+  DefaultInstrument (int x, int y, int w, int h)
+    : FGLayeredInstrument(x, y, w, h)
+  {
+    addLayer(new DefaultLayer());
+  }
+};
+
+
+/**
+ * Default panel: the default texture.
+ */
+class DefaultPanel : public FGPanel
+{
+public:
+  DefaultPanel (int x, int y, int w, int h) : FGPanel(x, y, w, h)
+  {
+    setBackground(defaultTexture.getTexture());
+  }
+};
+
+
+
+////////////////////////////////////////////////////////////////////////
+// Built-in layer for the magnetic compass ribbon layer.
+//
+// TODO: move this out into a special directory for built-in
+// layers of various sorts.
+////////////////////////////////////////////////////////////////////////
+
+class FGMagRibbon : public FGTexturedLayer
+{
+public:
+  FGMagRibbon (int w, int h);
+  virtual ~FGMagRibbon () {}
+
+  virtual void draw ();
+};
+
+FGMagRibbon::FGMagRibbon (int w, int h)
+  : FGTexturedLayer(w, h)
+{
+  FGCroppedTexture texture("Aircraft/c172/Instruments/Textures/compass-ribbon.rgb");
+  setTexture(texture);
+}
+
+void
+FGMagRibbon::draw ()
+{
+  double heading = FGSteam::get_MH_deg();
+  double xoffset, yoffset;
+
+  while (heading >= 360.0) {
+    heading -= 360.0;
+  }
+  while (heading < 0.0) {
+    heading += 360.0;
+  }
+
+  if (heading >= 60.0 && heading <= 180.0) {
+    xoffset = heading / 240.0;
+    yoffset = 0.75;
+  } else if (heading >= 150.0 && heading <= 270.0) {
+    xoffset = (heading - 90.0) / 240.0;
+    yoffset = 0.50;
+  } else if (heading >= 240.0 && heading <= 360.0) {
+    xoffset = (heading - 180.0) / 240.0;
+    yoffset = 0.25;
+  } else {
+    if (heading < 270.0)
+      heading += 360.0;
+    xoffset = (heading - 270.0) / 240.0;
+    yoffset = 0.0;
+  }
+
+  xoffset = 1.0 - xoffset;
+				// Adjust to put the number in the centre
+  xoffset -= 0.25;
 
-using std::istream;
-using std::string;
+  FGCroppedTexture &t = getTexture();
+  t.setCrop(xoffset, yoffset, xoffset + 0.5, yoffset + 0.25);
+  FGTexturedLayer::draw();
+}
 
 
 
 ////////////////////////////////////////////////////////////////////////
 // Read and construct a panel.
+//
+// The panel is specified as a regular property list, and each of the
+// instruments is its own, separate property list (and thus, a separate
+// XML document).  The functions in this section read in the files
+// as property lists, then extract properties to set up the panel
+// itself.
+//
+// A panel contains zero or more instruments.
+//
+// An instrument contains one or more layers and zero or more actions.
+//
+// A layer contains zero or more transformations.
+//
+// Some special types of layers also contain other objects, such as 
+// chunks of text or other layers.
+//
+// There are currently four types of layers:
+//
+// 1. Textured Layer (type="texture"), the default
+// 2. Text Layer (type="text")
+// 3. Switch Layer (type="switch")
+// 4. Built-in Layer (type="built-in", must also specify class)
+//
+// The only built-in layer so far is the ribbon for the magnetic compass
+// (class="compass-ribbon").
+//
+// There are three types of actions:
+//
+// 1. Adjust (type="adjust"), the default
+// 2. Swap (type="swap")
+// 3. Toggle (type="toggle")
+//
+// There are three types of transformations:
+//
+// 1. X shift (type="x-shift"), the default
+// 2. Y shift (type="y-shift")
+// 3. Rotation (type="rotation")
+//
+// Each of these may be associated with a property, so that a needle
+// will rotate with the airspeed, for example, or may have a fixed
+// floating-point value.
 ////////////////////////////////////////////////////////////////////////
 
 
 /**
- * Read a cropped texture.
+ * Read a cropped texture from the instrument's property list.
+ *
+ * The x1 and y1 properties give the starting position of the texture
+ * (between 0.0 and 1.0), and the the x2 and y2 properties give the
+ * ending position.  For example, to use the bottom-left quarter of a
+ * texture, x1=0.0, y1=0.0, x2=0.5, y2=0.5.
  */
-static CroppedTexture
-readTexture (SGPropertyNode node)
+static FGCroppedTexture
+readTexture (const SGPropertyNode * node)
 {
-  CroppedTexture texture(node.getStringValue("path"),
-			 node.getFloatValue("x1"),
-			 node.getFloatValue("y1"),
-			 node.getFloatValue("x2", 1.0),
-			 node.getFloatValue("y2", 1.0));
-  FG_LOG(FG_INPUT, FG_INFO, "Read texture " << node.getName());
+  FGCroppedTexture texture(node->getStringValue("path"),
+			   node->getFloatValue("x1"),
+			   node->getFloatValue("y1"),
+			   node->getFloatValue("x2", 1.0),
+			   node->getFloatValue("y2", 1.0));
+  FG_LOG(FG_INPUT, FG_INFO, "Read texture " << node->getName());
   return texture;
 }
 
 
 /**
- * Read an action.
+ * Read an action from the instrument's property list.
+ *
+ * The action will be performed when the user clicks a mouse button
+ * within the specified region of the instrument.  Actions always
+ * work by modifying the value of a property (see the SGValue class).
+ *
+ * The following action types are defined:
+ *
+ * "adjust" - modify the value of a floating-point property by
+ *    the increment specified.  This is the default.
+ *
+ * "swap" - swap the values of two-floating-point properties.
+ *
+ * "toggle" - toggle the value of a boolean property between true and
+ *    false.
+ *
+ * For the adjust action, it is possible to specify an increment
+ * (use a negative number for a decrement), a minimum allowed value,
+ * a maximum allowed value, and a flag to indicate whether the value
+ * should freeze or wrap-around when it reachs the minimum or maximum.
+ *
+ * The action will be scaled automatically if the instrument is not
+ * being drawn at its regular size.
  */
 static FGPanelAction *
-readAction (SGPropertyNode node)
+readAction (const SGPropertyNode * node, float hscale, float vscale)
 {
   FGPanelAction * action = 0;
 
-  cerr << "Reading action\n";
+  string name = node->getStringValue("name");
+  string type = node->getStringValue("type");
 
-  string type = node.getStringValue("type");
+  int button = node->getIntValue("button");
+  int x = int(node->getIntValue("x") * hscale);
+  int y = int(node->getIntValue("y") * vscale);
+  int w = int(node->getIntValue("w") * hscale);
+  int h = int(node->getIntValue("h") * vscale);
 
-  int button = node.getIntValue("button");
-  int x = node.getIntValue("x");
-  int y = node.getIntValue("y");
-  int w = node.getIntValue("w");
-  int h = node.getIntValue("h");
+  if (type == "") {
+    FG_LOG(FG_INPUT, FG_ALERT,
+	   "No type supplied for action " << name << " assuming \"adjust\"");
+    type = "adjust";
+  }
 
 				// Adjust a property value
   if (type == "adjust") {
-    string propName = node.getStringValue("property");
-    SGValue * value = current_properties.getValue(propName, true);
-    float increment = node.getFloatValue("increment", 1.0);
-    float min = node.getFloatValue("min", 0.0);
-    float max = node.getFloatValue("max", 0.0);
-    bool wrap = node.getBoolValue("wrap", false);
+    string propName = node->getStringValue("property");
+    SGValue * value = fgGetValue(propName, true);
+    float increment = node->getFloatValue("increment", 1.0);
+    float min = node->getFloatValue("min", 0.0);
+    float max = node->getFloatValue("max", 0.0);
+    bool wrap = node->getBoolValue("wrap", false);
     if (min == max)
-      FG_LOG(FG_INPUT, FG_ALERT, "Action " << node.getName()
+      FG_LOG(FG_INPUT, FG_ALERT, "Action " << node->getName()
 	     << " has same min and max value");
     action = new FGAdjustAction(button, x, y, w, h, value,
 				increment, min, max, wrap);
@@ -96,30 +290,23 @@ readAction (SGPropertyNode node)
 
 				// Swap two property values
   else if (type == "swap") {
-    string propName1 = node.getStringValue("property1");
-    string propName2 = node.getStringValue("property2");
-    SGValue * value1 = current_properties.getValue(propName1, true);
-    SGValue * value2 = current_properties.getValue(propName2, true);
+    string propName1 = node->getStringValue("property1");
+    string propName2 = node->getStringValue("property2");
+    SGValue * value1 = fgGetValue(propName1, true);
+    SGValue * value2 = fgGetValue(propName2, true);
     action = new FGSwapAction(button, x, y, w, h, value1, value2);
   } 
 
 				// Toggle a boolean value
   else if (type == "toggle") {
-    string propName = node.getStringValue("property");
-    SGValue * value = current_properties.getValue(propName, true);
+    string propName = node->getStringValue("property");
+    SGValue * value = fgGetValue(propName, true);
     action = new FGToggleAction(button, x, y, w, h, value);
   } 
 
-				// No type supplied
-  else if (type == "") {
-    FG_LOG(FG_INPUT, FG_ALERT, "No type specified for action "
-	   << node.getName());
-    return 0;
-  } 
-
 				// Unrecognized type
   else {
-    FG_LOG(FG_INPUT, FG_ALERT, "Unrecognized action type " << node.getName());
+    FG_LOG(FG_INPUT, FG_ALERT, "Unrecognized action type " << type);
     return 0;
   }
 
@@ -128,40 +315,82 @@ readAction (SGPropertyNode node)
 
 
 /**
- * Read a single transformation.
+ * Read a transformation from the instrument's property list.
+ *
+ * The panel module uses the transformations to slide or spin needles,
+ * knobs, and other indicators, and to place layers in the correct
+ * positions.  Every layer starts centered exactly on the x,y co-ordinate,
+ * and many layers need to be moved or rotated simply to display the
+ * instrument correctly.
+ *
+ * There are three types of transformations:
+ *
+ * "x-shift" - move the layer horizontally.
+ *
+ * "y-shift" - move the layer vertically.
+ *
+ * "rotation" - rotate the layer.
+ *
+ * Each transformation may have a fixed offset, and may also have
+ * a floating-point property value to add to the offset.  The
+ * floating-point property may be clamped to a minimum and/or
+ * maximum range and scaled (after clamping).
+ *
+ * Note that because of the way OpenGL works, transformations will
+ * appear to be applied backwards.
  */
 static FGPanelTransformation *
-readTransformation (SGPropertyNode node)
+readTransformation (const SGPropertyNode * node, float hscale, float vscale)
 {
   FGPanelTransformation * t = new FGPanelTransformation;
 
-  string name = node.getName();
-  string type = node.getStringValue("type");
-  string propName = node.getStringValue("property", "");
+  string name = node->getName();
+  string type = node->getStringValue("type");
+  string propName = node->getStringValue("property", "");
   SGValue * value = 0;
 
-  if (propName != "") {
-    value = current_properties.getValue(propName, true);
+  if (type == "") {
+    FG_LOG(FG_INPUT, FG_ALERT,
+	   "No type supplied for transformation " << name
+	   << " assuming \"rotation\"");
+    type = "rotation";
+  }
+
+  if (propName != (string)"") {
+    value = fgGetValue(propName, true);
   }
 
   t->value = value;
-  t->min = node.getFloatValue("min", 0.0);
-  t->max = node.getFloatValue("max", 1.0);
-  t->factor = node.getFloatValue("factor", 1.0);
-  t->offset = node.getFloatValue("offset", 0.0);
+  t->min = node->getFloatValue("min", -9999999);
+  t->max = node->getFloatValue("max", 99999999);
+  t->factor = node->getFloatValue("scale", 1.0);
+  t->offset = node->getFloatValue("offset", 0.0);
+
+				// Move the layer horizontally.
   if (type == "x-shift") {
     t->type = FGPanelTransformation::XSHIFT;
-  } else if (type == "y-shift") {
+    t->min *= hscale;
+    t->max *= hscale;
+    t->offset *= hscale;
+  } 
+
+				// Move the layer vertically.
+  else if (type == "y-shift") {
     t->type = FGPanelTransformation::YSHIFT;
-  } else if (type == "rotation") {
+    t->min *= vscale;
+    t->max *= vscale;
+    t->offset *= vscale;
+  } 
+
+				// Rotate the layer.  The rotation
+				// is in degrees, and does not need
+				// to scale with the instrument size.
+  else if (type == "rotation") {
     t->type = FGPanelTransformation::ROTATION;
-  } else if (type == "") {
-    FG_LOG(FG_INPUT, FG_ALERT,
-	   "'type' must be specified for transformation");
-    delete t;
-    return 0;
-  } else {
-    FG_LOG(FG_INPUT, FG_ALERT, "Unrecognized transformation: " << type);
+  } 
+
+  else {
+    FG_LOG(FG_INPUT, FG_ALERT, "Unrecognized transformation type " << type);
     delete t;
     return 0;
   }
@@ -172,117 +401,349 @@ readTransformation (SGPropertyNode node)
 
 
 /**
- * Read a single layer of an instrument.
+ * Read a chunk of text from the instrument's property list.
+ *
+ * A text layer consists of one or more chunks of text.  All chunks
+ * share the same font size and color (and eventually, font), but
+ * each can come from a different source.  There are three types of
+ * text chunks:
+ *
+ * "literal" - a literal text string (the default)
+ *
+ * "text-value" - the current value of a string property
+ *
+ * "number-value" - the current value of a floating-point property.
+ *
+ * All three may also include a printf-style format string.
+ */
+FGTextLayer::Chunk *
+readTextChunk (const SGPropertyNode * node)
+{
+  FGTextLayer::Chunk * chunk;
+  string name = node->getStringValue("name");
+  string type = node->getStringValue("type");
+  string format = node->getStringValue("format");
+
+				// Default to literal text.
+  if (type == "") {
+    FG_LOG(FG_INPUT, FG_INFO, "No type provided for text chunk " << name
+	   << " assuming \"literal\"");
+    type = "literal";
+  }
+
+				// A literal text string.
+  if (type == "literal") {
+    string text = node->getStringValue("text");
+    chunk = new FGTextLayer::Chunk(text, format);
+  }
+
+				// The value of a string property.
+  else if (type == "text-value") {
+    SGValue * value =
+      fgGetValue(node->getStringValue("property"), true);
+    chunk = new FGTextLayer::Chunk(FGTextLayer::TEXT_VALUE, value, format);
+  }
+
+				// The value of a float property.
+  else if (type == "number-value") {
+    string propName = node->getStringValue("property");
+    float scale = node->getFloatValue("scale", 1.0);
+    SGValue * value = fgGetValue(propName, true);
+    chunk = new FGTextLayer::Chunk(FGTextLayer::DOUBLE_VALUE, value,
+				   format, scale);
+  }
+
+				// Unknown type.
+  else {
+    FG_LOG(FG_INPUT, FG_ALERT, "Unrecognized type " << type
+	   << " for text chunk " << name);
+    return 0;
+  }
+
+  return chunk;
+}
+
+
+/**
+ * Read a single layer from an instrument's property list.
+ *
+ * Each instrument consists of one or more layers stacked on top
+ * of each other; the lower layers show through only where the upper
+ * layers contain an alpha component.  Each layer can be moved
+ * horizontally and vertically and rotated using transformations.
+ *
+ * This module currently recognizes four kinds of layers:
+ *
+ * "texture" - a layer containing a texture (the default)
+ *
+ * "text" - a layer containing text
+ *
+ * "switch" - a layer that switches between two other layers
+ *   based on the current value of a boolean property.
+ *
+ * "built-in" - a hard-coded layer supported by C++ code in FlightGear.
+ *
+ * Currently, the only built-in layer class is "compass-ribbon".
  */
 static FGInstrumentLayer *
-readLayer (SGPropertyNode node)
+readLayer (const SGPropertyNode * node, float hscale, float vscale)
 {
-  FGInstrumentLayer * l;
-  string name = node.getName();
+  FGInstrumentLayer * layer = NULL;
+  string name = node->getStringValue("name");
+  string type = node->getStringValue("type");
+  int w = node->getIntValue("w", -1);
+  int h = node->getIntValue("h", -1);
+  if (w != -1)
+    w = int(w * hscale);
+  if (h != -1)
+    h = int(h * vscale);
+
+
+  if (type == "") {
+    FG_LOG(FG_INPUT, FG_ALERT,
+	   "No type supplied for layer " << name
+	   << " assuming \"texture\"");
+    type = "texture";
+  }
 
-  CroppedTexture texture = readTexture(node.getSubNode("texture"));
-  l = new FGTexturedLayer(texture,
-			  node.getIntValue("w", -1),
-			  node.getIntValue("h", -1));
+
+				// A textured instrument layer.
+  if (type == "texture") {
+    FGCroppedTexture texture = readTexture(node->getNode("texture"));
+    layer = new FGTexturedLayer(texture, w, h);
+  }
+
+
+				// A textual instrument layer.
+  else if (type == "text") {
+    FGTextLayer * tlayer = new FGTextLayer(w, h); // FIXME
+
+				// Set the text color.
+    float red = node->getFloatValue("color/red", 0.0);
+    float green = node->getFloatValue("color/green", 0.0);
+    float blue = node->getFloatValue("color/blue", 0.0);
+    tlayer->setColor(red, green, blue);
+
+				// Set the point size.
+    float pointSize = node->getFloatValue("point-size", 10.0) * hscale;
+    tlayer->setPointSize(pointSize);
+
+				// Set the font.
+    // TODO
+
+    const SGPropertyNode * chunk_group = node->getNode("chunks");
+    if (chunk_group != 0) {
+      int nChunks = chunk_group->nChildren();
+      for (int i = 0; i < nChunks; i++) {
+	FGTextLayer::Chunk * chunk = readTextChunk(chunk_group->getChild(i));
+	if (chunk == 0) {
+	  delete layer;
+	  return 0;
+	}
+	tlayer->addChunk(chunk);
+      }
+      layer = tlayer;
+    }
+  }
+
+				// A switch instrument layer.
+  else if (type == "switch") {
+    SGValue * value =
+      fgGetValue(node->getStringValue("property"), true);
+    FGInstrumentLayer * layer1 =
+      readLayer(node->getNode("layer1"), hscale, vscale);
+    FGInstrumentLayer * layer2 =
+      readLayer(node->getNode("layer2"), hscale, vscale);
+    layer = new FGSwitchLayer(w, h, value, layer1, layer2);
+  }
+
+				// A built-in instrument layer.
+  else if (type == "built-in") {
+    string layerclass = node->getStringValue("class");
+
+    if (layerclass == "mag-ribbon") {
+      layer = new FGMagRibbon(w, h);
+    }
+
+    else if (layerclass == "") {
+      FG_LOG(FG_INPUT, FG_ALERT, "No class provided for built-in layer "
+	     << name);
+      return 0;
+    }
+
+    else {
+      FG_LOG(FG_INPUT, FG_ALERT, "Unknown built-in layer class "
+	     << layerclass);
+      return 0;
+    }
+  }
+
+				// An unknown type.
+  else {
+    FG_LOG(FG_INPUT, FG_ALERT, "Unrecognized layer type " << type);
+    delete layer;
+    return 0;
+  }
   
   //
   // Get the transformations for each layer.
   //
-  SGPropertyNode trans_group = node.getSubNode("transformations");
-  int nTransformations = trans_group.size();
-  for (int k = 0; k < nTransformations; k++) {
-    FGPanelTransformation * t = readTransformation(trans_group.getChild(k));
-    if (t == 0) {
-      delete l;
-      return 0;
+  const SGPropertyNode * trans_group = node->getNode("transformations");
+  if (trans_group != 0) {
+    int nTransformations = trans_group->nChildren();
+    for (int i = 0; i < nTransformations; i++) {
+      FGPanelTransformation * t = readTransformation(trans_group->getChild(i),
+						     hscale, vscale);
+      if (t == 0) {
+	delete layer;
+	return 0;
+      }
+      layer->addTransformation(t);
     }
-    l->addTransformation(t);
   }
   
   FG_LOG(FG_INPUT, FG_INFO, "Read layer " << name);
-  return l;
+  return layer;
 }
 
 
 /**
- * Read an instrument.
+ * Read an instrument from a property list.
+ *
+ * The instrument consists of a preferred width and height
+ * (the panel may override these), together with a list of layers
+ * and a list of actions to be performed when the user clicks 
+ * the mouse over the instrument.  All co-ordinates are relative
+ * to the instrument's position, so instruments are fully relocatable;
+ * likewise, co-ordinates for actions and transformations will be
+ * scaled automatically if the instrument is not at its preferred size.
  */
 static FGPanelInstrument *
-readInstrument (SGPropertyNode node)
+readInstrument (const SGPropertyNode * node, int x, int y,
+		int real_w, int real_h)
 {
-  const string &name = node.getStringValue("name");
+  int w = node->getIntValue("w");
+  int h = node->getIntValue("h");
+  const string &name = node->getStringValue("name");
+
+  float hscale = 1.0;
+  float vscale = 1.0;
+  if (real_w != -1) {
+    hscale = float(real_w) / float(w);
+    w = real_w;
+  }
+  if (real_h != -1) {
+    vscale = float(real_h) / float(h);
+    h = real_h;
+  }
 
   FG_LOG(FG_INPUT, FG_INFO, "Reading instrument " << name);
 
   FGLayeredInstrument * instrument =
-    new FGLayeredInstrument(0, 0,
-			    node.getIntValue("w"),
-			    node.getIntValue("h"));
+    new FGLayeredInstrument(x, y, w, h);
 
   //
   // Get the actions for the instrument.
   //
-  SGPropertyNode action_group = node.getSubNode("actions");
-  int nActions = action_group.size();
-  cerr << "There are " << nActions << " actions\n";
-  for (int j = 0; j < nActions; j++) {
-    FGPanelAction * action = readAction(action_group.getChild(j));
-    if (action == 0) {
-      delete instrument;
-      return 0;
+  const SGPropertyNode * action_group = node->getNode("actions");
+  if (action_group != 0) {
+    int nActions = action_group->nChildren();
+    for (int i = 0; i < nActions; i++) {
+      FGPanelAction * action = readAction(action_group->getChild(i),
+					  hscale, vscale);
+      if (action == 0) {
+	delete instrument;
+	return new DefaultInstrument(x, y, w, h);
+      }
+      instrument->addAction(action);
     }
-    instrument->addAction(action);
   }
 
   //
   // Get the layers for the instrument.
   //
-  SGPropertyNode layer_group = node.getSubNode("layers");
-  int nLayers = layer_group.size();
-  for (int j = 0; j < nLayers; j++) {
-    FGInstrumentLayer * layer = readLayer(layer_group.getChild(j));
-    if (layer == 0) {
-      delete instrument;
-      return 0;
+  const SGPropertyNode * layer_group = node->getNode("layers");
+  if (layer_group != 0) {
+    int nLayers = layer_group->nChildren();
+    for (int i = 0; i < nLayers; i++) {
+      FGInstrumentLayer * layer = readLayer(layer_group->getChild(i),
+					    hscale, vscale);
+      if (layer == 0) {
+	delete instrument;
+	return new DefaultInstrument(x, y, w, h);
+      }
+      instrument->addLayer(layer);
     }
-    instrument->addLayer(layer);
   }
-
+    
   FG_LOG(FG_INPUT, FG_INFO, "Done reading instrument " << name);
   return instrument;
 }
 
 
 /**
- * Read a property list defining an instrument panel.
+ * Read a panel from a property list.
+ *
+ * Each panel instrument will appear in its own, separate
+ * property list.  The top level simply names the panel and
+ * places the instruments in their appropriate locations (and
+ * optionally resizes them if necessary).
  *
  * Returns 0 if the read fails for any reason.
  */
 FGPanel *
 fgReadPanel (istream &input)
 {
-  SGPropertyList props;
+  SGPropertyNode root;
 
 
   //
   // Read the property list from disk.
   //
-  if (!readPropertyList(input, &props)) {
+  if (!readProperties(input, &root)) {
     FG_LOG(FG_INPUT, FG_ALERT, "Malformed property list for panel.");
     return 0;
   }
   FG_LOG(FG_INPUT, FG_INFO, "Read properties for panel " <<
-	 props.getStringValue("/name"));
+	 root.getStringValue("name"));
 
   //
   // Construct a new, empty panel.
   //
   FGPanel * panel = new FGPanel(0, 0, 1024, 768);// FIXME: use variable size
 
+
+  //
+  // Grab the panel's dimensions, default to 1024x443.
+  //
+  int panel_w = (root.hasValue("w") ? root.getIntValue("w") : 1024);
+  int panel_h = (root.hasValue("h") ? root.getIntValue("h") : 443);
+  panel->setWidth(panel_w);
+  panel->setHeight(panel_h);
+
+  //
+  // Grab the visible external viewing area, default to 
+  //
+  panel->setViewHeight(root.hasValue("view-height") ?
+		       root.getIntValue("view-height") :
+		       768 - panel_h + 2);
+
+  //
+  // Grab the panel's initial offsets, default to 0, 0.
+  //
+  int xoffset = (root.hasValue("x-offset") ?
+		 root.getIntValue("x-offset") :
+		 0);
+  int yoffset = (root.hasValue("y-offset") ?
+		 root.getIntValue("y-offset") :
+		 0);
+  panel->setXOffset(xoffset);
+  panel->setYOffset(yoffset);
+
   //
   // Assign the background texture, if any, or a bogus chequerboard.
   //
-  string bgTexture = props.getStringValue("/background");
+  string bgTexture = root.getStringValue("background");
   if (bgTexture == "")
     bgTexture = "FOO";
   panel->setBackground(FGTextureManager::createTexture(bgTexture.c_str()));
@@ -293,37 +754,46 @@ fgReadPanel (istream &input)
   // Create each instrument.
   //
   FG_LOG(FG_INPUT, FG_INFO, "Reading panel instruments");
-  SGPropertyNode instrument_group("/instruments", &props);
-  int nInstruments = instrument_group.size();
-  for (int i = 0; i < nInstruments; i++) {
-    SGPropertyList props2;
-    SGPropertyNode node = instrument_group.getChild(i);
-
-    string path = node.getStringValue("path");
-    int x = node.getIntValue("x");
-    int y = node.getIntValue("y");
-    int w = node.getIntValue("w");
-    int h = node.getIntValue("h");
-
-    FG_LOG(FG_INPUT, FG_INFO, "Reading instrument "
-	   << node.getName()
-	   << " from "
-	   << path);
-
-    if (!readPropertyList(path, &props2)) {
-      delete panel;
-      return 0;
-    }
-
-    FGPanelInstrument * instrument =
-      readInstrument(SGPropertyNode("/", &props2));
-    if (instrument == 0) {
-      delete instrument;
-      delete panel;
-      return 0;
+  const SGPropertyNode * instrument_group = root.getChild("instruments");
+  if (instrument_group != 0) {
+    int nInstruments = instrument_group->nChildren();
+    for (int i = 0; i < nInstruments; i++) {
+      const SGPropertyNode * node = instrument_group->getChild(i);
+      
+      FGPath path( globals->get_fg_root() );
+      path.append(node->getStringValue("path"));
+      
+      FG_LOG(FG_INPUT, FG_INFO, "Reading instrument "
+	     << node->getName()
+	     << " from "
+	     << path.str());
+      
+      int x = node->getIntValue("x", -1);
+      int y = node->getIntValue("y", -1);
+      int w = node->getIntValue("w", -1);
+      int h = node->getIntValue("h", -1);
+      
+      if (x == -1 || y == -1) {
+	FG_LOG(FG_INPUT, FG_ALERT, "x and y positions must be specified and >0");
+	delete panel;
+	return 0;
+      }
+
+				// Read the instrument from
+				// a separate file.
+      FGPanelInstrument * instrument = 0;
+      
+      SGPropertyNode root2;
+      
+      if (readProperties(path.str(), &root2)) {
+	cerr << "Read " << root2.nChildren() << " top-level nodes from "
+	     << path.c_str() << endl;
+	instrument = readInstrument(&root2, x, y, w, h);
+      }
+      if (instrument == 0)
+	instrument = new DefaultInstrument(x, y, w, h);
+      panel->addInstrument(instrument);
     }
-    instrument->setPosition(x, y);
-    panel->addInstrument(instrument);
   }
   FG_LOG(FG_INPUT, FG_INFO, "Done reading panel instruments");
 
@@ -335,4 +805,31 @@ fgReadPanel (istream &input)
 }
 
 
+/**
+ * Read a panel from a property list.
+ *
+ * This function opens a stream to a file, then invokes the
+ * main fgReadPanel() function.
+ */
+FGPanel *
+fgReadPanel (const string &relative_path)
+{
+  FGPanel * panel = 0;
+  FGPath path(globals->get_fg_root());
+  path.append(relative_path);
+  ifstream input(path.c_str());
+  if (!input.good()) {
+    FG_LOG(FG_INPUT, FG_ALERT,
+	   "Cannot read panel configuration from " << path.str());
+  } else {
+    panel = fgReadPanel(input);
+    input.close();
+  }
+  if (panel == 0)
+    panel = new DefaultPanel(0, 0, 1024, 768);
+  return panel;
+}
+
+
+
 // end of panel_io.cxx