render_gpu: Add hints for debug and low-power preference

include/SDL3/SDL_hints.h

@@ -2772,6 +2772,34 @@ extern "C" {
  */
 #define SDL_HINT_RENDER_VULKAN_DEBUG "SDL_RENDER_VULKAN_DEBUG"
 
+/**
+ * A variable controlling whether to create the GPU device in debug mode.
+ *
+ * This variable can be set to the following values:
+ *
+ * - "0": Disable debug mode use (default)
+ * - "1": Enable debug mode use
+ *
+ * This hint should be set before creating a renderer.
+ *
+ * \since This hint is available since SDL 3.0.0.
+ */
+#define SDL_HINT_RENDER_GPU_DEBUG "SDL_RENDER_GPU_DEBUG"
+
+/**
+ * A variable controlling whether to prefer a low-power GPU on multi-GPU systems.
+ *
+ * This variable can be set to the following values:
+ *
+ * - "0": Prefer high-performance GPU (default)
+ * - "1": Prefer low-power GPU
+ *
+ * This hint should be set before creating a renderer.
+ *
+ * \since This hint is available since SDL 3.0.0.
+ */
+#define SDL_HINT_RENDER_GPU_LOW_POWER "SDL_RENDER_GPU_LOW_POWER"
+
 /**
  * A variable specifying which render driver to use.
  *

src/render/sdlgpu/SDL_render_gpu.c

@@ -1163,7 +1163,16 @@ static int GPU_CreateRenderer(SDL_Renderer *renderer, SDL_Window *window, SDL_Pr
         goto error;
     }
 
-    SDL_SetBooleanProperty(create_props, SDL_PROP_GPU_CREATEDEVICE_DEBUGMODE_BOOL, SDL_TRUE);
+    SDL_bool debug = SDL_GetBooleanProperty(create_props, SDL_PROP_GPU_CREATEDEVICE_DEBUGMODE_BOOL, SDL_FALSE);
+    SDL_bool lowpower = SDL_GetBooleanProperty(create_props, SDL_PROP_GPU_CREATEDEVICE_PREFERLOWPOWER_BOOL, SDL_FALSE);
+
+    // Prefer environment variables/hints if they exist, otherwise defer to properties
+    debug = SDL_GetHintBoolean(SDL_HINT_RENDER_GPU_DEBUG, debug);
+    lowpower = SDL_GetHintBoolean(SDL_HINT_RENDER_GPU_LOW_POWER, lowpower);
+
+    SDL_SetBooleanProperty(create_props, SDL_PROP_GPU_CREATEDEVICE_DEBUGMODE_BOOL, debug);
+    SDL_SetBooleanProperty(create_props, SDL_PROP_GPU_CREATEDEVICE_PREFERLOWPOWER_BOOL, lowpower);
+
     GPU_FillSupportedShaderFormats(create_props);
     data->device = SDL_GpuCreateDeviceWithProperties(create_props);