DisplayMode: Prefer to keep the refresh rate near the original rate

skyjake · Mar 22, 2012 · b6a71b4 · b6a71b4
1 parent 8bd9331
commit b6a71b4
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Showing 2 changed files with 20 additions and 5 deletions.
diff --git a/doomsday/engine/portable/src/canvas.cpp b/doomsday/engine/portable/src/canvas.cpp
@@ -2,6 +2,9 @@
  * @file canvas.cpp
  * OpenGL drawing surface implementation. @ingroup gl
  *
+ * @todo Merge mouse_qt.c with this source file since the mouse tracking
+ * functionality is implemented here.
+ *
  * @authors Copyright (c) 2012 Jaakko Keränen <jaakko.keranen@iki.fi>
  *
  * @par License

diff --git a/doomsday/engine/portable/src/displaymode.cpp b/doomsday/engine/portable/src/displaymode.cpp
@@ -57,6 +57,8 @@ static bool reduce(int& ratioX, int& ratioY)
 }
 #endif
 
+static float differenceToOriginalHz(float hz);
+
 struct Mode : public DisplayMode
 {
     Mode()
@@ -102,8 +104,8 @@ struct Mode : public DisplayMode
             {
                 if(depth == b.depth)
                 {
-                    // Biggest refresh rate first.
-                    return refreshRate > b.refreshRate;
+                    // The refresh rate that more closely matches the original is preferable.
+                    return differenceToOriginalHz(refreshRate) < differenceToOriginalHz(b.refreshRate);
                 }
                 return depth < b.depth;
             }
@@ -163,25 +165,31 @@ struct Mode : public DisplayMode
     }
 };
 
-typedef std::set<Mode> Modes;
+typedef std::set<Mode> Modes; // note: no duplicates
 static Modes modes;
 static Mode originalMode;
 static bool captured;
 
+static float differenceToOriginalHz(float hz)
+{
+    return qAbs(hz - originalMode.refreshRate);
+}
+
 int DisplayMode_Init(void)
 {
     if(inited) return true;
 
     captured = false;
     DisplayMode_Native_Init();
 
+    // This is used for sorting the mode set (Hz).
+    originalMode = Mode::fromCurrent();
+
     for(int i = 0; i < DisplayMode_Native_Count(); ++i)
     {
         modes.insert(Mode(i));
     }
 
-    originalMode = Mode::fromCurrent();
-
 #ifdef _DEBUG
     qDebug() << "Current mode is:";
     originalMode.debugPrint();
@@ -265,6 +273,10 @@ const DisplayMode* DisplayMode_FindClosest(int width, int height, int depth, flo
             score += squared(i->refreshRate - freq);
         }
 
+        // Note: The first mode to hit the lowest score wins; if there are many modes
+        // with the same score, the first one will be chosen. Particularly if the
+        // frequency has not been specified, the sort order of the modes defines which
+        // one is picked.
         if(!best || score < bestScore)
         {
             /*