DisplayManagerWin: fix a little bit more and harder

So tha backwards conversion of the refresh rate in isModeMatching was
wrong. Our "fudged" refreshRate mode needs to be rounded down to get to
the DEVMODEW rate, not up.

Completely redo this: add a function to convert DEVMODEW to our own
DMVideoMode, and do the comparison always on DMVideoMode. (The use of
fabs() in modeEquals() is just a safe guard in case of relaxed float
semantics are used instead of strict IEEE semantics. Oh, and no, I'm not
implementing DMVideoMode::operator== - I'd just add more new bugs.)

src/display/win/DisplayManagerWin.cpp

@@ -7,10 +7,40 @@
 //
 
 #include <QRect>
+#include <math.h>
 
 #include "QsLog.h"
 #include "DisplayManagerWin.h"
 
+///////////////////////////////////////////////////////////////////////////////////////////////////
+static DMVideoMode convertDevMode(const DEVMODEW& devmode)
+{
+  DMVideoMode mode = {};
+  mode.height = devmode.dmPelsHeight;
+  mode.width = devmode.dmPelsWidth;
+  mode.refreshRate = devmode.dmDisplayFrequency;
+  mode.bitsPerPixel = devmode.dmBitsPerPel;
+  mode.interlaced = !!(devmode.dmDisplayFlags & DM_INTERLACED);
+
+  // Windows just returns integer refresh rate so let's fudge it
+  if (mode.refreshRate == 59 ||
+      mode.refreshRate == 29 ||
+      mode.refreshRate == 23)
+      mode.refreshRate = (float)(mode.refreshRate + 1) / 1.001f;
+
+  return mode;
+}
+
+///////////////////////////////////////////////////////////////////////////////////////////////////
+static bool modeEquals(const DMVideoMode& m1, const DMVideoMode& m2)
+{
+  return m1.height == m2.height &&
+         m1.width == m2.width &&
+         fabs(m1.refreshRate - m2.refreshRate) < 1e9 &&
+         m1.bitsPerPixel == m2.bitsPerPixel &&
+         m1.interlaced == m2.interlaced;
+}
+
 ///////////////////////////////////////////////////////////////////////////////////////////////////
 bool DisplayManagerWin::initialize()
 {
@@ -38,23 +68,10 @@ bool DisplayManagerWin::initialize()
       {
         // add the videomode to the display
         DMVideoModePtr videoMode = DMVideoModePtr(new DMVideoMode);
+        *videoMode = convertDevMode(modeInfo);
         videoMode->id = modeId;
         display->videoModes[videoMode->id] = videoMode;
 
-        // setup mode information
-        videoMode->height = modeInfo.dmPelsHeight;
-        videoMode->width = modeInfo.dmPelsWidth;
-        videoMode->refreshRate = modeInfo.dmDisplayFrequency;
-        videoMode->bitsPerPixel = modeInfo.dmBitsPerPel;
-        videoMode->interlaced = (modeInfo.dmDisplayFlags & DM_INTERLACED) ? true : false;
-
-        // Windows just returns interger refresh rate so
-        // let's fudge it
-        if (videoMode->refreshRate == 59 ||
-            videoMode->refreshRate == 29 ||
-            videoMode->refreshRate == 23)
-           videoMode->refreshRate = (float)(videoMode->refreshRate + 1) / 1.001f;
-
         modeId++;
       }
     }
@@ -119,10 +136,12 @@ int DisplayManagerWin::getCurrentDisplayMode(int display)
     return -1;
   }
 
+  DMVideoMode mode = convertDevMode(modeInfo);
+
   // check if current mode info matches on of our modes
   for (int modeId = 0; modeId < displays[display]->videoModes.size(); modeId++)
   {
-    if (isModeMatching(modeInfo, displays[display]->videoModes[modeId]))
+    if (modeEquals(mode, *displays[display]->videoModes[modeId]))
       return modeId;
   }
 
@@ -196,20 +215,3 @@ bool DisplayManagerWin::getModeInfo(int display, int mode, DEVMODEW& info)
 
   return false;
 }
-
-///////////////////////////////////////////////////////////////////////////////////////////////////
-bool DisplayManagerWin::isModeMatching(DEVMODEW& modeInfo, DMVideoModePtr videoMode)
-{
-  if (videoMode->height != modeInfo.dmPelsHeight)
-    return false;
-  if (videoMode->width != modeInfo.dmPelsWidth)
-    return false;
-  if ((int)(videoMode->refreshRate + 0.5f) != modeInfo.dmDisplayFrequency)
-    return false;
-  if (videoMode->bitsPerPixel != modeInfo.dmBitsPerPel)
-    return false;
-  if (videoMode->interlaced != ((modeInfo.dmDisplayFlags & DM_INTERLACED) ? true : false))
-    return false;
-
-  return true;
-}

src/display/win/DisplayManagerWin.h

@@ -12,7 +12,6 @@ class DisplayManagerWin : public DisplayManager
 private:
   bool getDisplayInfo(int display, DISPLAY_DEVICEW& info);
   bool getModeInfo(int display, int mode, DEVMODEW& info);
-  bool isModeMatching(DEVMODEW& modeInfo, DMVideoModePtr videoMode);
 
   QMap<int, QString> m_displayAdapters;