Fix: Data races on cursor state in OpenGL backends

5 files changed, 25 insertions, 8 deletions

diff --git a/src/video/cocoa/cocoa_ogl.mm b/src/video/cocoa/cocoa_ogl.mm
index 8d02428e0..f8c2e97e0 100644
--- a/src/video/cocoa/cocoa_ogl.mm
+++ b/src/video/cocoa/cocoa_ogl.mm
@@ -134,7 +134,7 @@ static bool _allowSoftware;
 	CGLSetCurrentContext(ctx);
 
 	OpenGLBackend::Get()->Paint();
-	if (_cursor.in_window) OpenGLBackend::Get()->DrawMouseCursor();
+	OpenGLBackend::Get()->DrawMouseCursor();
 
 	[ super drawInCGLContext:ctx pixelFormat:pf forLayerTime:t displayTime:ts ];
 }
diff --git a/src/video/opengl.cpp b/src/video/opengl.cpp
index c346fd152..c1c1afaae 100644
--- a/src/video/opengl.cpp
+++ b/src/video/opengl.cpp
@@ -1053,18 +1053,20 @@ void OpenGLBackend::Paint()
  */
 void OpenGLBackend::DrawMouseCursor()
 {
+	if (!this->cursor_in_window) return;
+
 	/* Draw cursor on screen */
 	_cur_dpi = &_screen;
-	for (uint i = 0; i < _cursor.sprite_count; ++i) {
-		SpriteID sprite = _cursor.sprite_seq[i].sprite;
+	for (uint i = 0; i < this->cursor_sprite_count; ++i) {
+		SpriteID sprite = this->cursor_sprite_seq[i].sprite;
 
 		/* Sprites are cached by PopulateCursorCache(). */
 		if (this->cursor_cache.Contains(sprite)) {
 			Sprite *spr = this->cursor_cache.Get(sprite);
 
-			this->RenderOglSprite((OpenGLSprite *)spr->data, _cursor.sprite_seq[i].pal,
-					_cursor.pos.x + _cursor.sprite_pos[i].x + UnScaleByZoom(spr->x_offs, ZOOM_LVL_GUI),
-					_cursor.pos.y + _cursor.sprite_pos[i].y + UnScaleByZoom(spr->y_offs, ZOOM_LVL_GUI),
+			this->RenderOglSprite((OpenGLSprite *)spr->data, this->cursor_sprite_seq[i].pal,
+					this->cursor_pos.x + this->cursor_sprite_pos[i].x + UnScaleByZoom(spr->x_offs, ZOOM_LVL_GUI),
+					this->cursor_pos.y + this->cursor_sprite_pos[i].y + UnScaleByZoom(spr->y_offs, ZOOM_LVL_GUI),
 					ZOOM_LVL_GUI);
 		}
 	}
@@ -1072,6 +1074,9 @@ void OpenGLBackend::DrawMouseCursor()
 
 void OpenGLBackend::PopulateCursorCache()
 {
+	static_assert(lengthof(_cursor.sprite_seq) == lengthof(this->cursor_sprite_seq));
+	static_assert(lengthof(_cursor.sprite_pos) == lengthof(this->cursor_sprite_pos));
+
 	if (this->clear_cursor_cache) {
 		/* We have a pending cursor cache clear to do first. */
 		this->clear_cursor_cache = false;
@@ -1085,7 +1090,13 @@ void OpenGLBackend::PopulateCursorCache()
 		}
 	}
 
+	this->cursor_pos = _cursor.pos;
+	this->cursor_sprite_count = _cursor.sprite_count;
+	this->cursor_in_window = _cursor.in_window;
+
 	for (uint i = 0; i < _cursor.sprite_count; ++i) {
+		this->cursor_sprite_seq[i] = _cursor.sprite_seq[i];
+		this->cursor_sprite_pos[i] = _cursor.sprite_pos[i];
 		SpriteID sprite = _cursor.sprite_seq[i].sprite;
 
 		if (!this->cursor_cache.Contains(sprite)) {
diff --git a/src/video/opengl.h b/src/video/opengl.h
index c17a8536d..7e42b20be 100644
--- a/src/video/opengl.h
+++ b/src/video/opengl.h
@@ -65,6 +65,12 @@ private:
 	PaletteID last_sprite_pal = (PaletteID)-1; ///< Last uploaded remap palette.
 	bool clear_cursor_cache = false;           ///< A clear of the cursor cache is pending.
 
+	Point cursor_pos;                    ///< Cursor position
+	bool cursor_in_window;               ///< Cursor inside this window
+	PalSpriteID cursor_sprite_seq[16];   ///< Current image of cursor
+	Point cursor_sprite_pos[16];         ///< Relative position of individual cursor sprites
+	uint cursor_sprite_count;            ///< Number of cursor sprites to draw
+
 	OpenGLBackend();
 	~OpenGLBackend();
 
diff --git a/src/video/sdl2_opengl_v.cpp b/src/video/sdl2_opengl_v.cpp
index 86dc104dd..5df283751 100644
--- a/src/video/sdl2_opengl_v.cpp
+++ b/src/video/sdl2_opengl_v.cpp
@@ -174,7 +174,7 @@ void VideoDriver_SDL_OpenGL::Paint()
 	}
 
 	OpenGLBackend::Get()->Paint();
-	if (_cursor.in_window) OpenGLBackend::Get()->DrawMouseCursor();
+	OpenGLBackend::Get()->DrawMouseCursor();
 
 	SDL_GL_SwapWindow(this->sdl_window);
 }
diff --git a/src/video/win32_v.cpp b/src/video/win32_v.cpp
index b4d3946ea..426d74c0a 100644
--- a/src/video/win32_v.cpp
+++ b/src/video/win32_v.cpp
@@ -1454,7 +1454,7 @@ void VideoDriver_Win32OpenGL::Paint()
 	}
 
 	OpenGLBackend::Get()->Paint();
-	if (_cursor.in_window) OpenGLBackend::Get()->DrawMouseCursor();
+	OpenGLBackend::Get()->DrawMouseCursor();
 
 	SwapBuffers(this->dc);
 }