Added offscreen rendering via WindowBuffer to remove drawing flicker

src/GameWindow.c

@@ -27,8 +27,12 @@ void GameWindow_Init(GameWindow *pGameWindow)
     // Load snd resources
     Sounds_Init(&(pGameWindow->Sounds));
     
-    // Set port for first draw
+    // Initialize window buffer
+    WindowBuffer_Init(&(pGameWindow->WindowBuffer), pGameWindow->Window);
+    
+    // Setup graphics before first draw
     SetPort(pGameWindow->Window);
+    FillRect(&(pGameWindow->Window->portRect), WindowPattern);
     
     GameWindow_SetScene(pGameWindow, Title);
 }
@@ -38,9 +42,10 @@ void GameWindow_Draw(const GameWindow *pGameWindow, bool fullRefresh)
     GrafPtr oldPort;
     const Rect *pContentRect = &(pGameWindow->Window->portRect);
     
+    // Save the current port
     GetPort(&oldPort);
     
-    SetPort(pGameWindow->Window);
+    WindowBuffer_StartDraw(&(pGameWindow->WindowBuffer));
     
     if (fullRefresh)
     {
@@ -64,6 +69,8 @@ void GameWindow_Draw(const GameWindow *pGameWindow, bool fullRefresh)
             break;
     }
     
+    WindowBuffer_EndDraw(&(pGameWindow->WindowBuffer));
+    
     SetPort(oldPort);
 }
 

src/GameWindow.h

@@ -5,6 +5,7 @@
 #define GAMEWINDOW_H
 
 #include "MacCommon.h"
+#include "WindowBuffer.h"
 #include "GameEngine.h"
 #include "Bitmaps.h"
 #include "Sounds.h"
@@ -15,6 +16,7 @@
 typedef struct sGameWindow
 {
     WindowPtr     Window;
+    WindowBuffer  WindowBuffer;
     GameEngine    Engine;
     Bitmaps       Bitmaps;
     Sounds        Sounds;

src/LevelEndScene.c

@@ -85,13 +85,12 @@ void LevelEndScene_Click(GameWindow *pGameWindow, const Point *pPosition)
 {
     if (PtInRect(*pPosition, &(pGameWindow->LevelEndScene.RetryButtonRect)))
     {
-        Sounds_PlayRetrySnd(&(pGameWindow->Sounds));
         GameEngine_ResetLevel(&(pGameWindow->Engine));
         GameWindow_SetScene(pGameWindow, Play);
+        Sounds_PlayRetrySnd(&(pGameWindow->Sounds));
     }
     else if (PtInRect(*pPosition, &(pGameWindow->LevelEndScene.NextButtonRect)))
     {
-        Sounds_PlayClickSnd(&(pGameWindow->Sounds));
         GameEngine_NextLevel(&(pGameWindow->Engine));
         
         if (GameEngine_IsGameOver(&(pGameWindow->Engine)))

src/PlayScene.c

@@ -161,9 +161,9 @@ void PlayScene_Click(GameWindow *pGameWindow, const Point *pPosition)
                 
                 if (PtInRect(*pPosition, &lightRect))
                 {
-                    Sounds_PlayClickSnd(&(pGameWindow->Sounds));
                     GameEngine_ToggleLights(&(pGameWindow->Engine), c, r);
                     GameWindow_Draw(pGameWindow, false);
+                    Sounds_PlayClickSnd(&(pGameWindow->Sounds));
                     break;
                 }
             }
@@ -183,9 +183,9 @@ void PlayScene_Click(GameWindow *pGameWindow, const Point *pPosition)
         
         if (PtInRect(*pPosition, &(pGameWindow->PlayScene.RetryButtonRect)))
         {
-            Sounds_PlayRetrySnd(&(pGameWindow->Sounds));
             GameEngine_ResetLevel(&(pGameWindow->Engine));
             GameWindow_Draw(pGameWindow, false);
+            Sounds_PlayRetrySnd(&(pGameWindow->Sounds));
         }
         else if (PtInRect(*pPosition, &(pGameWindow->PlayScene.SoundButtonRect)))
         {

src/TitleScene.c

@@ -54,13 +54,11 @@ void TitleScene_Click(GameWindow *pGameWindow, const Point *pPosition)
 {
     if (PtInRect(*pPosition, &(pGameWindow->TitleScene.SetARect)))
     {
-        Sounds_PlayClickSnd(&(pGameWindow->Sounds));
         GameEngine_NewGame(&(pGameWindow->Engine), false);
         GameWindow_SetScene(pGameWindow, Play);
     }
     else if (PtInRect(*pPosition, &(pGameWindow->TitleScene.SetBRect)))
     {
-        Sounds_PlayClickSnd(&(pGameWindow->Sounds));
         GameEngine_NewGame(&(pGameWindow->Engine), true);
         GameWindow_SetScene(pGameWindow, Play);
     }

src/WindowBuffer.c

@@ -0,0 +1,56 @@
+// Copyright (c) Jon Thysell <http://jonthysell.com>
+// Licensed under the MIT License.
+
+#include "WindowBuffer.h"
+#include "MacCommon.h"
+
+void WindowBuffer_Init(WindowBuffer *pWindowBuffer, const WindowPtr window)
+{
+    int16_t width, height;
+    BitMap newBits;
+    
+    pWindowBuffer->Window = window;
+    
+    // Create a BitMap as the backing for the buffer,
+    // since System 6 doesn't have fancy GWorlds
+    width = window->portRect.right - window->portRect.left;
+    height = window->portRect.bottom - window->portRect.top;
+    SetRect(&newBits.bounds, 0, 0, width, height);
+    newBits.rowBytes = ((width + 31)/32) * 4;
+    newBits.baseAddr = NewPtr(height * newBits.rowBytes);
+    
+    // Clear the bitmap
+    CopyBits(&newBits,
+             &newBits,
+             &newBits.bounds,
+             &newBits.bounds,
+             srcXor,
+             nil);
+    
+    // Create the buffer and get it ready
+    pWindowBuffer->Buffer = (GrafPtr)NewPtr(sizeof(GrafPort));
+    OpenPort(pWindowBuffer->Buffer);
+    SetPort(pWindowBuffer->Buffer);
+    
+    pWindowBuffer->Buffer->portRect = newBits.bounds;
+    RectRgn(pWindowBuffer->Buffer->visRgn, &newBits.bounds);
+    SetPortBits(&newBits);
+}
+
+void WindowBuffer_StartDraw(const WindowBuffer *pWindowBuffer)
+{
+    // Set the buffer as the port for future QuickDraw commands
+    SetPort(pWindowBuffer->Buffer);
+}
+
+void WindowBuffer_EndDraw(const WindowBuffer *pWindowBuffer)
+{
+    SetPort(pWindowBuffer->Window);
+    
+    // Copy the buffer to the window
+    CopyBits(&(pWindowBuffer->Buffer->portBits),
+             &(pWindowBuffer->Window->portBits),
+             &(pWindowBuffer->Buffer->portRect),
+             &(pWindowBuffer->Window->portRect),
+             srcCopy, nil);
+}

src/WindowBuffer.h

@@ -0,0 +1,17 @@
+// Copyright (c) Jon Thysell <http://jonthysell.com>
+// Licensed under the MIT License.
+
+#ifndef WINDOWBUFFER_H
+#define WINDOWBUFFER_H
+
+typedef struct sWindowBuffer
+{
+    WindowPtr Window;
+    GrafPtr   Buffer;
+} WindowBuffer;
+
+void WindowBuffer_Init(WindowBuffer *pWindowBuffer, const WindowPtr window);
+void WindowBuffer_StartDraw(const WindowBuffer *pWindowBuffer);
+void WindowBuffer_EndDraw(const WindowBuffer *pWindowBuffer);
+
+#endif