Mac: Don't -[NSOpenGLContext update] on (potentially) the wrong thread.

If the user is using their context from a non-main thread, we could be calling -[NSOpenGLContext update] on our thread, while they were accessing it on their thread. With this change, we schedule updates when the event comes in on the main thread, and act on them when the user calls SDL_GL_MakeCurrent or SDL_GL_SwapWindow.
libsdl-org · Aug 7, 2013 · 879053c · 879053c
1 parent 4804438
commit 879053c
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Showing 4 changed files with 74 additions and 31 deletions.
diff --git a/src/video/cocoa/SDL_cocoaopengl.h b/src/video/cocoa/SDL_cocoaopengl.h
@@ -25,11 +25,26 @@
 
 #if SDL_VIDEO_OPENGL_CGL
 
+#include "SDL_atomic.h"
+#import <Cocoa/Cocoa.h>
+
 struct SDL_GLDriverData
 {
     int initialized;
 };
 
+@interface SDLOpenGLContext : NSOpenGLContext {
+    SDL_atomic_t dirty;
+}
+
+- (id)initWithFormat:(NSOpenGLPixelFormat *)format
+        shareContext:(NSOpenGLContext *)share;
+- (void)scheduleUpdate;
+- (void)updateIfNeeded;
+
+@end
+
+
 /* OpenGL functions */
 extern int Cocoa_GL_LoadLibrary(_THIS, const char *path);
 extern void *Cocoa_GL_GetProcAddress(_THIS, const char *proc);

diff --git a/src/video/cocoa/SDL_cocoaopengl.m b/src/video/cocoa/SDL_cocoaopengl.m
@@ -24,6 +24,7 @@
 
 #if SDL_VIDEO_OPENGL_CGL
 #include "SDL_cocoavideo.h"
+#include "SDL_cocoaopengl.h"
 
 #include <OpenGL/CGLTypes.h>
 #include <OpenGL/OpenGL.h>
@@ -45,6 +46,40 @@
 #define kCGLOGLPVersion_3_2_Core 0x3200
 #endif
 
+@implementation SDLOpenGLContext : NSOpenGLContext
+
+- (id)initWithFormat:(NSOpenGLPixelFormat *)format
+        shareContext:(NSOpenGLContext *)share
+{
+    SDL_AtomicSet(&self->dirty, 0);
+    return [super initWithFormat:format shareContext:share];
+}
+
+- (void)scheduleUpdate
+{
+    SDL_AtomicAdd(&self->dirty, 1);
+}
+
+/* This should only be called on the thread on which a user is using the context. */
+- (void)updateIfNeeded
+{
+    int value = SDL_AtomicSet(&self->dirty, 0);
+    if (value > 0) {
+        /* We call the real underlying update here, since -[SDLOpenGLContext update] just calls us. */
+        [super update];
+    }
+}
+
+/* This should only be called on the thread on which a user is using the context. */
+- (void)update
+{
+    /* This ensures that regular 'update' calls clear the atomic dirty flag. */
+    [self scheduleUpdate];
+    [self updateIfNeeded];
+}
+
+@end
+
 
 int
 Cocoa_GL_LoadLibrary(_THIS, const char *path)
@@ -89,7 +124,7 @@
     SDL_DisplayData *displaydata = (SDL_DisplayData *)display->driverdata;
     NSOpenGLPixelFormatAttribute attr[32];
     NSOpenGLPixelFormat *fmt;
-    NSOpenGLContext *context;
+    SDLOpenGLContext *context;
     NSOpenGLContext *share_context = nil;
     int i = 0;
 
@@ -181,7 +216,7 @@
         share_context = (NSOpenGLContext*)SDL_GL_GetCurrentContext();
     }
 
-    context = [[NSOpenGLContext alloc] initWithFormat:fmt shareContext:share_context];
+    context = [[SDLOpenGLContext alloc] initWithFormat:fmt shareContext:share_context];
 
     [fmt release];
 
@@ -210,13 +245,14 @@
 
     if (context) {
         SDL_WindowData *windowdata = (SDL_WindowData *)window->driverdata;
-        NSOpenGLContext *nscontext = (NSOpenGLContext *)context;
-
+        SDLOpenGLContext *nscontext = (SDLOpenGLContext *)context;
         windowdata->nscontext = nscontext;
         if ([nscontext view] != [windowdata->nswindow contentView]) {
             [nscontext setView:[windowdata->nswindow contentView]];
-            [nscontext update];
+            [nscontext scheduleUpdate];
         }
+
+        [nscontext updateIfNeeded];
         [nscontext makeCurrentContext];
     } else {
         [NSOpenGLContext clearCurrentContext];
@@ -236,7 +272,7 @@
 
     pool = [[NSAutoreleasePool alloc] init];
 
-    nscontext = [NSOpenGLContext currentContext];
+    nscontext = (NSOpenGLContext*)SDL_GL_GetCurrentContext();
     if (nscontext != nil) {
         value = interval;
         [nscontext setValues:&value forParameter:NSOpenGLCPSwapInterval];
@@ -259,7 +295,7 @@
 
     pool = [[NSAutoreleasePool alloc] init];
 
-    nscontext = [NSOpenGLContext currentContext];
+    nscontext = (NSOpenGLContext*)SDL_GL_GetCurrentContext();
     if (nscontext != nil) {
         [nscontext getValues:&value forParameter:NSOpenGLCPSwapInterval];
         status = (int)value;
@@ -274,11 +310,12 @@
 {
     NSAutoreleasePool *pool;
     SDL_WindowData *windowdata = (SDL_WindowData *)window->driverdata;
-    NSOpenGLContext *nscontext = windowdata->nscontext;
+    SDLOpenGLContext *nscontext = windowdata->nscontext;
 
     pool = [[NSAutoreleasePool alloc] init];
 
     [nscontext flushBuffer];
+    [nscontext updateIfNeeded];
 
     [pool release];
 }

diff --git a/src/video/cocoa/SDL_cocoawindow.h b/src/video/cocoa/SDL_cocoawindow.h
@@ -77,11 +77,13 @@ typedef enum {
 @end
 /* *INDENT-ON* */
 
+@class SDLOpenGLContext;
+
 struct SDL_WindowData
 {
     SDL_Window *window;
     NSWindow *nswindow;
-    NSOpenGLContext *nscontext;
+    SDLOpenGLContext *nscontext;
     SDL_bool created;
     Cocoa_WindowListener *listener;
     struct SDL_VideoData *videodata;

diff --git a/src/video/cocoa/SDL_cocoawindow.m b/src/video/cocoa/SDL_cocoawindow.m
@@ -32,6 +32,7 @@
 #include "SDL_cocoavideo.h"
 #include "SDL_cocoashape.h"
 #include "SDL_cocoamouse.h"
+#include "SDL_cocoaopengl.h"
 
 
 static Uint32 s_moveHack;
@@ -187,7 +188,6 @@ - (void)windowDidExpose:(NSNotification *)aNotification
 - (void)windowDidMove:(NSNotification *)aNotification
 {
     int x, y;
-    SDL_VideoDevice *device = SDL_GetVideoDevice();
     SDL_Window *window = _data->window;
     NSWindow *nswindow = _data->nswindow;
     NSRect rect = [nswindow contentRectForFrameRect:[nswindow frame]];
@@ -211,16 +211,13 @@ - (void)windowDidMove:(NSNotification *)aNotification
     x = (int)rect.origin.x;
     y = (int)rect.origin.y;
 
-    if (window == device->current_glwin) {
-        [((NSOpenGLContext *) device->current_glctx) update];
-    }
+    [_data->nscontext scheduleUpdate];
 
     SDL_SendWindowEvent(window, SDL_WINDOWEVENT_MOVED, x, y);
 }
 
 - (void)windowDidResize:(NSNotification *)aNotification
 {
-    SDL_VideoDevice *device = SDL_GetVideoDevice();
     int x, y, w, h;
     NSRect rect = [_data->nswindow contentRectForFrameRect:[_data->nswindow frame]];
     ConvertNSRect(&rect);
@@ -231,9 +228,7 @@ - (void)windowDidResize:(NSNotification *)aNotification
     if (SDL_IsShapedWindow(_data->window))
         Cocoa_ResizeWindowShape(_data->window);
 
-    if (_data->window == device->current_glwin) {
-        [((NSOpenGLContext *) device->current_glctx) update];
-    }
+    [_data->nscontext scheduleUpdate];
 
     /* The window can move during a resize event, such as when maximizing
        or resizing from a corner */
@@ -788,7 +783,8 @@ - (void)resetCursorRects
 Cocoa_SetWindowPosition(_THIS, SDL_Window * window)
 {
     NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
-    NSWindow *nswindow = ((SDL_WindowData *) window->driverdata)->nswindow;
+    SDL_WindowData *windata = (SDL_WindowData *) window->driverdata;
+    NSWindow *nswindow = windata->nswindow;
     NSRect rect;
     Uint32 moveHack;
 
@@ -803,9 +799,7 @@ - (void)resetCursorRects
     [nswindow setFrameOrigin:rect.origin];
     s_moveHack = moveHack;
 
-    if (window == _this->current_glwin) {
-        [((NSOpenGLContext *) _this->current_glctx) update];
-    }
+    [windata->nscontext scheduleUpdate];
 
     [pool release];
 }
@@ -822,9 +816,7 @@ - (void)resetCursorRects
     size.height = window->h;
     [nswindow setContentSize:size];
 
-    if (window == _this->current_glwin) {
-        [((NSOpenGLContext *) _this->current_glctx) update];
-    }
+    [windata->nscontext scheduleUpdate];
 
     [pool release];
 }
@@ -906,13 +898,12 @@ - (void)resetCursorRects
 Cocoa_MaximizeWindow(_THIS, SDL_Window * window)
 {
     NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
-    NSWindow *nswindow = ((SDL_WindowData *) window->driverdata)->nswindow;
+    SDL_WindowData *windata = (SDL_WindowData *) window->driverdata;
+    NSWindow *nswindow = windata->nswindow;
 
     [nswindow zoom:nil];
 
-    if (window == _this->current_glwin) {
-        [((NSOpenGLContext *) _this->current_glctx) update];
-    }
+    [windata->nscontext scheduleUpdate];
 
     [pool release];
 }
@@ -1049,9 +1040,7 @@ - (void)resetCursorRects
     [nswindow makeKeyAndOrderFront:nil];
     [data->listener resumeVisibleObservation];
 
-    if (window == _this->current_glwin) {
-        [((NSOpenGLContext *) _this->current_glctx) update];
-    }
+    [data->nscontext scheduleUpdate];
 
     [pool release];
 }