Add option to flush mouse messages from message queue after repositioning the cursor

Author: benstone

inc/utestres.h

@@ -53,6 +53,7 @@
 #define IDC_CHECK2 1026
 #define IDC_CHECK3 1027
 #define IDC_CHECK4 1028
+#define IDC_CHECK5 1029
 #define cidInfo 40038
 #define cidWriteBmps 40039
 #define cidHelpBook 40040

kauai/src/appb.cpp

@@ -267,6 +267,21 @@ void APPB::PositionCurs(long xpScreen, long ypScreen)
 
     // REVIEW shonk: implement on Mac
     MacWin(RawRtn(), SetCursorPos(xpScreen, ypScreen));
+
+#ifdef WIN
+    if (_fFlushCursor)
+    {
+        // APPB::TrackMouse gets the mouse position by peeking the message queue for WM_MOUSE* messages.
+        // After the cursor position has been reset, there may still be some WM_MOUSEMOVE messages with old
+        // cooordinates in the message queue. This can cause jitter when dragging actors around the stage.
+        // Flush all mouse move messages from this thread's message queue.
+        MSG msg;
+        while (PeekMessage(&msg, hNil, WM_MOUSEFIRST, WM_MOUSELAST, PM_REMOVE | PM_NOYIELD))
+        {
+            // do nothing
+        }
+    }
+#endif // WIN
 }
 
 /***************************************************************************
@@ -548,6 +563,7 @@ bool APPB::_FInit(ulong grfapp, ulong grfgob, long ginDef)
     AssertThis(0);
 
     _fOffscreen = FPure(grfapp & fappOffscreen);
+    _fFlushCursor = fTrue;
 
 #ifdef DEBUG
     if (!_FInitDebug())
@@ -1418,6 +1434,10 @@ bool APPB::FSetProp(long prid, long lw)
         ResetToolTip();
         break;
 
+    case kpridReduceMouseJitter:
+        _fFlushCursor = FPure(lw);
+        break;
+
     default:
         return _FSetProp(prid, lw);
     }
@@ -1454,6 +1474,10 @@ bool APPB::FGetProp(long prid, long *plw)
         *plw = LwMulDivAway(_dtsToolTip, kdtimSecond, kdtsSecond);
         break;
 
+    case kpridReduceMouseJitter:
+        *plw = FPure(_fFlushCursor);
+        break;
+
     default:
         if (!_FFindProp(prid, &prop))
             return fFalse;

kauai/src/appb.h

@@ -104,6 +104,7 @@ class APPB : public APPB_PAR
     bool _fToolTip : 1;         // whether we're in tool-tip mode
     bool _fForeground : 1;      // whether we're the foreground app
     bool _fEndModal : 1;        // set to end the topmost modal loop
+    bool _fFlushCursor : 1;     // flush cursor events when setting cursor position
 
     PGL _pglmkrgn;        // list of marked regions for fast updating
     long _onnDefFixed;    // default fixed pitch font

kauai/src/framedef.h

@@ -86,6 +86,7 @@
 #define kpridMaximized 1
 #define kpridFullScreen 2
 #define kpridToolTipDelay 3
+#define kpridReduceMouseJitter 4
 
 /***************************************************************************
     Transitions that Kauai knows how to do.

src/studio/utest.cpp

@@ -3261,6 +3261,8 @@ enum
     iditStartupSound,
     iditStereoSound,
     iditHighQualitySoundImport,
+    iditReduceMouseJitter,
+
     iditLimInfo
 };
 
@@ -3336,6 +3338,10 @@ bool APP::FCmdInfo(PCMD pcmd)
     AssertDo(FGetProp(kpridHighQualitySoundImport, &lwValue), "can't get sound import property");
     pdlg->PutCheck(iditHighQualitySoundImport, FPure(lwValue));
 
+    lwValue = 0;
+    AssertDo(FGetProp(kpridReduceMouseJitter, &lwValue), "can't get reduce mouse jitter property");
+    pdlg->PutCheck(iditReduceMouseJitter, FPure(lwValue));
+
     // Show dialog
     idit = pdlg->IditDo();
 
@@ -3445,6 +3451,9 @@ bool APP::FCmdInfo(PCMD pcmd)
     fValue = pdlg->FGetCheck(iditHighQualitySoundImport);
     AssertDo(FSetProp(kpridHighQualitySoundImport, fValue), "can't save sound import property");
 
+    fValue = pdlg->FGetCheck(iditReduceMouseJitter);
+    AssertDo(FSetProp(kpridReduceMouseJitter, fValue), "can't save reduce mouse jitter property");
+
     if (fSaveChanges)
     {
         AssertDo(FGetProp(kpridHighQualitySoundImport, &lwValue), "can't get sound import property");
@@ -3454,6 +3463,8 @@ bool APP::FCmdInfo(PCMD pcmd)
         AssertDo(FGetProp(kpridStereoSoundPlayback, &lwValue), "can't get stereo sound property");
         AssertDo(FGetSetRegKey(kszStereoSound, &lwValue, size(lwValue), fregSetKey),
                  "can't save stereo sound preference to registry");
+
+        // TODO: Save "flush mouse" property to the registry
     }
 
     ReleasePpo(&pdlg);

src/studio/utest.rc

@@ -199,6 +199,7 @@ BEGIN
     CONTROL         "Play startup sound",IDC_CHECK2,"Button",BS_AUTOCHECKBOX | WS_TABSTOP,12,102,174,12
     CONTROL         "Stereo sound playback (requires restart)",IDC_CHECK3,"Button",BS_AUTOCHECKBOX | WS_TABSTOP,12,120,174,12
     CONTROL         "High quality sound import",IDC_CHECK4,"Button",BS_AUTOCHECKBOX | WS_TABSTOP,12,138,174,12
+    CONTROL         "Reduce mouse jitter (experimental)",IDC_CHECK5,"Button",BS_AUTOCHECKBOX | WS_TABSTOP,12,156,174,12
 END
 
 dlidInitFailed DIALOG DISCARDABLE  0, 0, 187, 71