Improve get_current_texture for window resizing (#705)

* Improve get_current_texture for window resizing

* dont present when using dummy tex

* warn on successive fails

* small fix

* correct

* Wrap up

* codegen

Author: almarklein

wgpu/_classes.py

@@ -448,13 +448,12 @@ def _create_texture_bitmap(self):
         # Note that the label 'present' is used by read_texture() to determine
         # that it can use a shared copy buffer.
         device = self._config["device"]
-        self._texture = device.create_texture(
+        return device.create_texture(
             label="present",
             size=(width, height, 1),
             format=self._config["format"],
             usage=self._config["usage"] | flags.TextureUsage.COPY_SRC,
         )
-        return self._texture
 
     def _create_texture_screen(self):
         raise NotImplementedError()

wgpu/backends/wgpu_native/_api.py

@@ -674,6 +674,8 @@ class GPUCanvasContext(classes.GPUCanvasContext):
     # the more cryptic Rust panics.
 
     _surface_id = ffi.NULL
+    _wgpu_config = None
+    _skip_present_screen = False
 
     def __init__(self, canvas, present_methods):
         super().__init__(canvas, present_methods)
@@ -685,6 +687,9 @@ def __init__(self, canvas, present_methods):
         else:  # method == "bitmap"
             self._surface_id = ffi.NULL
 
+        # A stat for get_current_texture
+        self._number_of_successive_unsuccesful_textures = 0
+
     def _get_capabilities_screen(self, adapter):
         adapter_id = adapter._internal
         surface_id = self._surface_id
@@ -815,6 +820,7 @@ def _configure_screen(
         c_present_mode = getattr(lib, f"WGPUPresentMode_{present_mode.capitalize()}")
 
         # Prepare config object
+        width, height = self._get_canvas().get_physical_size()
 
         # H: nextInChain: WGPUChainedStruct *, device: WGPUDevice, format: WGPUTextureFormat, usage: WGPUTextureUsage/int, width: int, height: int, viewFormatCount: int, viewFormats: WGPUTextureFormat *, alphaMode: WGPUCompositeAlphaMode, presentMode: WGPUPresentMode
         self._wgpu_config = new_struct_p(
@@ -826,52 +832,70 @@ def _configure_screen(
             viewFormatCount=len(view_formats),
             viewFormats=c_view_formats,
             alphaMode=c_alpha_mode,
-            width=0,
-            height=0,
             presentMode=c_present_mode,
+            width=width,  # overriden elsewhere in this class
+            height=height,  # overriden elsewhere in this class
         )
 
-    def _configure_screen_real(self, width, height):
+        # Configure now (if possible)
+        self._configure_screen_real()
+
+    def _configure_screen_real(self):
         # If a texture is still active, better release it first
         self._drop_texture()
-        # Set the size
-        self._wgpu_config.width = width
-        self._wgpu_config.height = height
-        if width <= 0 or height <= 0:
-            raise RuntimeError(
-                "Cannot configure canvas that has no pixels ({width}x{height})."
-            )
         # Configure, and store the config if we did not error out
-        if self._surface_id:
+        if (
+            self._surface_id
+            and self._wgpu_config.width > 0
+            and self._wgpu_config.height > 0
+        ):
             # H: void f(WGPUSurface surface, WGPUSurfaceConfiguration const * config)
             libf.wgpuSurfaceConfigure(self._surface_id, self._wgpu_config)
+        else:
+            # Set size to zero, to trigger auto-configure later
+            self._wgpu_config.width = 0
 
     def _unconfigure_screen(self):
         if self._surface_id:
             # H: void f(WGPUSurface surface)
             libf.wgpuSurfaceUnconfigure(self._surface_id)
+            self._wgpu_config = None
 
     def _create_texture_screen(self):
-        surface_id = self._surface_id
+        # Check
+        if self._surface_id is None:
+            raise RuntimeError("Looks like the CanvasContext is already destroyed.")
+        if self._wgpu_config is None:
+            raise RuntimeError(
+                "Cannot get surface texture because the CanvasContext has not yet been configured."
+            )
 
-        # Reconfigure when the canvas has resized.
-        # On some systems (Windows+Qt) this is not necessary, because
-        # the texture status would be Outdated below, resulting in a
-        # reconfigure. But on others (e.g. glfwf) the texture size does
-        # not have to match the window size, apparently. The downside
-        # for doing this check on the former systems, is that errors
-        # get logged, which would not be there if we did not
-        # pre-emptively reconfigure. These log entries are harmless but
-        # annoying, and I currently don't know how to prevent them
-        # elegantly. See issue #352
+        # When the window size has changed, we need to reconfigure. If we wouldn't:
+        #
+        # * On some systems (seen on MacOS with glfw and Qt) the texture status that we get below
+        #   will happily report 'SuccessOptimal', even when the the window has resized, and the
+        #   texture will simply be stretched to fit the window. I believe this can be considered a bug.
+        # * On other systems (seen on Windows and Linux) the texture status would report 'SuccessSuboptimal',
+        #   and the texture will either be stretched (Windows) or blitted to the window leaving either
+        #   part of the texture invisible, or making part of the window black/transparent (Linux).
+        # * On some systems the texture status is 'Outdated' even if we do set the size. We deal with
+        #   that by providing a dummy texture, and warn when this happens too often in succession.
+
+        # Get size info
         old_size = (self._wgpu_config.width, self._wgpu_config.height)
         new_size = tuple(self._get_canvas().get_physical_size())
-        if old_size != new_size:
-            self._configure_screen_real(*new_size)
-
-        # Try to obtain a texture.
-        # `If it fails, depending on status, we reconfigure and try again.
-
+        if new_size[0] <= 0 or new_size[1] <= 0:
+            # It's the responsibility of the drawing /scheduling logic to prevent this case.
+            raise RuntimeError("Cannot get texture for a canvas with zero pixels.")
+
+        # Re-configure when the size has changed.
+        if new_size != old_size:
+            self._wgpu_config.width = new_size[0]
+            self._wgpu_config.height = new_size[1]
+            self._configure_screen_real()
+
+        # Prepare for obtaining a texture.
+        status_str_map = enum_int2str["SurfaceGetCurrentTextureStatus"]
         # H: nextInChain: WGPUChainedStructOut *, texture: WGPUTexture, status: WGPUSurfaceGetCurrentTextureStatus
         surface_texture = new_struct_p(
             "WGPUSurfaceTexture *",
@@ -880,41 +904,65 @@ def _create_texture_screen(self):
             # not used: status
         )
 
-        for attempt in [1, 2]:
-            # H: void f(WGPUSurface surface, WGPUSurfaceTexture * surfaceTexture)
-            libf.wgpuSurfaceGetCurrentTexture(surface_id, surface_texture)
-            status_int = surface_texture.status
-            status_str = enum_int2str["SurfaceGetCurrentTextureStatus"].get(
-                status_int, "Unknown"
-            )
-            texture_id = surface_texture.texture
-            if status_int == lib.WGPUSurfaceGetCurrentTextureStatus_SuccessOptimal:
-                break  # Yay! Everything is good and we can render this frame.
-            elif status_int == lib.WGPUSurfaceGetCurrentTextureStatus_SuccessSuboptimal:
-                # Still OK - the surface can present the frame, but in a suboptimal way. The surface may need reconfiguration.
-                logger.warning("The surface texture is suboptimal.")
-                break
+        # Try to obtain texture
+        # H: void f(WGPUSurface surface, WGPUSurfaceTexture * surfaceTexture)
+        libf.wgpuSurfaceGetCurrentTexture(self._surface_id, surface_texture)
+        status_int = surface_texture.status
+        status_str = status_str_map.get(status_int, "Unknown")
+        texture_id = surface_texture.texture
+
+        if status_int == lib.WGPUSurfaceGetCurrentTextureStatus_SuccessOptimal:
+            # Yay! Everything is good and we can render this frame.
+            self._number_of_successive_unsuccesful_textures = 0
+        elif status_int in [
+            lib.WGPUSurfaceGetCurrentTextureStatus_SuccessSuboptimal,
+            lib.WGPUSurfaceGetCurrentTextureStatus_Timeout,
+            lib.WGPUSurfaceGetCurrentTextureStatus_Outdated,
+            lib.WGPUSurfaceGetCurrentTextureStatus_Lost,
+        ]:
             if texture_id:
                 # H: void f(WGPUTexture texture)
                 libf.wgpuTextureRelease(texture_id)
-            if attempt == 1 and status_int in [
+                texture_id = 0
+            # Try to re-configure, if we can
+            self._configure_screen_real()
+            # H: void f(WGPUSurface surface, WGPUSurfaceTexture * surfaceTexture)
+            libf.wgpuSurfaceGetCurrentTexture(self._surface_id, surface_texture)
+            status_int = surface_texture.status
+            status_str = status_str_map.get(status_int, "Unknown")
+            texture_id = surface_texture.texture
+
+        # If still not optimal, we need to make some decisions ...
+        if status_int != lib.WGPUSurfaceGetCurrentTextureStatus_SuccessOptimal:
+            # It's ok if we miss a sporadic frame during resizing, but warn if it becomes too much.
+            self._number_of_successive_unsuccesful_textures += 1
+            if self._number_of_successive_unsuccesful_textures > 5:
+                n = self._number_of_successive_unsuccesful_textures
+                self._number_of_successive_unsuccesful_textures = 0
+                logger.warning(
+                    f"No succesful surface texture obtained for {n} frames: {status_str!r}"
+                )
+            # Decide what to do
+            if status_int == lib.WGPUSurfaceGetCurrentTextureStatus_SuccessSuboptimal:
+                # Can still use the texture
+                pass
+            elif status_int in [
                 lib.WGPUSurfaceGetCurrentTextureStatus_Timeout,
                 lib.WGPUSurfaceGetCurrentTextureStatus_Outdated,
                 lib.WGPUSurfaceGetCurrentTextureStatus_Lost,
             ]:
-                # Configure and try again.
-                # On Window+Qt this happens e.g. when the window has resized
-                # (status==Outdated), but also when moving the window from one
-                # monitor to another with different scale-factor.
-                logger.info(
-                    f"Re-configuring canvas context, because {status_str} ({status_int})."
-                )
-                self._configure_screen_real(*new_size)
+                # Use a dummy texture that we cannot present
+                if texture_id:
+                    # H: void f(WGPUTexture texture)
+                    libf.wgpuTextureRelease(texture_id)
+                    texture_id = 0
+                self._skip_present_screen = True
+                return self._create_texture_bitmap()
             else:
                 # WGPUSurfaceGetCurrentTextureStatus_OutOfMemory
                 # WGPUSurfaceGetCurrentTextureStatus_DeviceLost
                 # WGPUSurfaceGetCurrentTextureStatus_Error
-                # Or if this is the second attempt.
+                # This is something we cannot recover from.
                 raise RuntimeError(
                     f"Cannot get surface texture: {status_str} ({status_int})."
                 )
@@ -959,15 +1007,17 @@ def _create_texture_screen(self):
             "format": format,
             "usage": usage,
         }
-
         device = self._config["device"]
         return GPUTexture(label, texture_id, device, tex_info)
 
     def _present_screen(self):
-        # H: WGPUStatus f(WGPUSurface surface)
-        status = libf.wgpuSurfacePresent(self._surface_id)
-        if status != lib.WGPUStatus_Success:
-            raise RuntimeError("Error calling wgpuSurfacePresent")
+        if self._skip_present_screen:
+            self._skip_present_screen = False
+        else:
+            # H: WGPUStatus f(WGPUSurface surface)
+            status = libf.wgpuSurfacePresent(self._surface_id)
+            if status != lib.WGPUStatus_Success:
+                logger.warning("wgpuSurfacePresent failed")
 
     def _release(self):
         self._drop_texture()

wgpu/resources/codegen_report.md

@@ -29,6 +29,6 @@
 * Enum CanvasAlphaMode missing in wgpu.h
 * Enum CanvasToneMappingMode missing in wgpu.h
 * Wrote 255 enum mappings and 47 struct-field mappings to wgpu_native/_mappings.py
-* Validated 149 C function calls
+* Validated 151 C function calls
 * Not using 69 C functions
 * Validated 95 C structs