Merge pull request #459 from cosmic-utils/fix/blur-rotation-aspect-letterbox

fix(blur): correct aspect on rotated sensors and paint letterbox

Author: FreddyFunk

src/app/camera_preview/widget.rs

@@ -125,6 +125,14 @@ impl AppModel {
             let zoom_level = self.current_zoom_level();
             let scroll_zoom_enabled = self.mode.supports_fit_and_zoom();
 
+            // Look up the COSMIC theme's window background color. The blur
+            // shader paints letterbox areas with this so the preview's
+            // out-of-image region matches the app background instead of
+            // letting the window bg leak through (issue: white letterbox
+            // during Fit-mode blur transitions).
+            let bg = cosmic::theme::active().cosmic().bg_color();
+            let letterbox_color = [bg.red, bg.green, bg.blue, 1.0];
+
             let video_elem = video_widget::video_widget(
                 frame.clone(),
                 video_widget::VideoWidgetConfig {
@@ -140,6 +148,7 @@ impl AppModel {
                     cover_blend: Some(cover_blend),
                     bar_top_px: self.top_ui_height(),
                     bar_bottom_px: self.bottom_ui_height(),
+                    letterbox_color,
                 },
             );
 

src/app/filter_picker/view.rs

@@ -88,6 +88,9 @@ impl AppModel {
                         cover_blend: None,
                         bar_top_px: 0.0,
                         bar_bottom_px: 0.0,
+                        // Filter previews don't use blur, so this is only here
+                        // to satisfy the struct — value is ignored downstream.
+                        letterbox_color: [0.0, 0.0, 0.0, 1.0],
                     },
                 )
             } else {

src/app/handlers/capture.rs

@@ -559,6 +559,16 @@ impl AppModel {
             "Burst mode frames collected, starting processing"
         );
 
+        // Capture blur state up front so the HDR+ processing blur shows the
+        // burst still frame with the rotation/mirror of the camera that
+        // produced it. Without this, `blur_frame_rotation` keeps whatever
+        // value was set the last time a transition fired — or `None` if the
+        // user never switched cameras this session — and the burst frame
+        // renders rotated wrong on 90°/270° sensors. Mirrors the existing
+        // capture in `handle_burst_mode_complete`.
+        self.blur_frame_rotation = self.current_frame_rotation;
+        self.blur_frame_mirror = self.should_mirror_preview();
+
         // Turn off flash now that capture is complete (before processing)
         self.turn_off_flash_hardware();
         if self.flash.active {

src/app/video_primitive.rs

@@ -120,6 +120,17 @@ struct ViewportUniform {
     bar_top_height: f32,
     /// Bottom bar height in pixels
     bar_bottom_height: f32,
+    /// Padding to align `letterbox_color` (vec4) to 16 bytes — required for the
+    /// struct to round-trip through wgpu's std140-ish uniform layout. Two
+    /// `f32`s after the three trailing `f32` fields above bring us to offset
+    /// 80, which is a vec4 boundary.
+    _pad0: f32,
+    _pad1: f32,
+    /// Theme background color (RGBA, sRGB straight) used by the blur shader
+    /// to fill letterbox areas instead of returning transparent (which would
+    /// let the COSMIC window background show through during Fit-mode blur
+    /// transitions). Other shaders accept the field but ignore it.
+    letterbox_color: [f32; 4],
 }
 
 /// Combined frame and viewport data to reduce mutex contention
@@ -156,6 +167,10 @@ pub struct VideoPrimitive {
     pub crop_uv: Option<(f32, f32, f32, f32)>,
     /// Zoom level (1.0 = no zoom, 2.0 = 2x zoom, etc.)
     pub zoom_level: f32,
+    /// Theme background color (sRGB straight, RGBA) — passed to the blur
+    /// shader so the letterbox in Contain / Fit mode is painted with the
+    /// app background instead of leaking through to the COSMIC window bg.
+    pub letterbox_color: [f32; 4],
 }
 
 /// Video texture (shared across filter variations)
@@ -272,6 +287,10 @@ impl VideoPrimitive {
             rotation: 0,
             crop_uv: None,
             zoom_level: 1.0,
+            // Black is a sensible default if no widget overrides it (e.g.
+            // headless tests). The real bg color is plumbed in via
+            // `VideoWidgetConfig::letterbox_color` from the active theme.
+            letterbox_color: [0.0, 0.0, 0.0, 1.0],
         }
     }
 
@@ -396,14 +415,28 @@ impl PrimitiveTrait for VideoPrimitive {
 
                 // For blur video (VIDEO_ID_BLUR), ensure intermediate textures exist
                 // and invalidate the blur cache so the new frame gets blurred.
+                //
+                // The blur pass 1 shader is configured with viewport_size in
+                // **display orientation** (sensor w/h swapped for 90°/270°
+                // rotation) so its Contain math computes the right aspect.
+                // The intermediate render target must match that orientation
+                // — otherwise the shader thinks it's drawing into a portrait
+                // viewport while wgpu rasterises to a landscape target, and
+                // the blur frame comes out stretched on rotated sensors
+                // (visible on the Pixel 3a / 90° mount).
                 if self.video_id == VIDEO_ID_BLUR {
                     pipeline
                         .blur_cached
                         .store(false, std::sync::atomic::Ordering::Relaxed);
+                    let (int_w, int_h) = if self.rotation == 1 || self.rotation == 3 {
+                        (frame.height, frame.width)
+                    } else {
+                        (frame.width, frame.height)
+                    };
                     pipeline.ensure_intermediate_textures(
                         device,
-                        frame.width,
-                        frame.height,
+                        int_w,
+                        int_h,
                         pipeline.output_format,
                     );
                 }
@@ -484,6 +517,9 @@ impl PrimitiveTrait for VideoPrimitive {
                             rotation: self.rotation,
                             bar_top_height: 0.0,
                             bar_bottom_height: 0.0,
+                            _pad0: 0.0,
+                            _pad1: 0.0,
+                            letterbox_color: self.letterbox_color,
                         };
                         queue.write_buffer(
                             &binding.viewport_buffer,
@@ -507,6 +543,9 @@ impl PrimitiveTrait for VideoPrimitive {
                         rotation: self.rotation,
                         bar_top_height: bar_top,
                         bar_bottom_height: bar_bottom,
+                        _pad0: 0.0,
+                        _pad1: 0.0,
+                        letterbox_color: self.letterbox_color,
                     };
                     queue.write_buffer(
                         &binding.viewport_buffer,
@@ -586,6 +625,9 @@ impl PrimitiveTrait for VideoPrimitive {
                             rotation: 0,     // Already rotated in preblur
                             bar_top_height: 0.0,
                             bar_bottom_height: 0.0,
+                            _pad0: 0.0,
+                            _pad1: 0.0,
+                            letterbox_color: self.letterbox_color,
                         };
                         queue.write_buffer(
                             &pb_binding.viewport_buffer,
@@ -614,6 +656,9 @@ impl PrimitiveTrait for VideoPrimitive {
                         rotation: 0,     // Already rotated in pass 1
                         bar_top_height: 0.0,
                         bar_bottom_height: 0.0,
+                        _pad0: 0.0,
+                        _pad1: 0.0,
+                        letterbox_color: self.letterbox_color,
                     };
                     queue.write_buffer(
                         &intermediate_1.viewport_buffer,
@@ -639,6 +684,9 @@ impl PrimitiveTrait for VideoPrimitive {
                         rotation: 0,     // Already rotated in pass 1
                         bar_top_height: bar_top,
                         bar_bottom_height: bar_bottom,
+                        _pad0: 0.0,
+                        _pad1: 0.0,
+                        letterbox_color: self.letterbox_color,
                     };
                     queue.write_buffer(
                         &intermediate_2.viewport_buffer,

src/app/video_shader.wgsl

@@ -22,6 +22,9 @@ struct ViewportUniform {
     rotation: u32,              // Sensor rotation: 0=None, 1=90CW, 2=180, 3=270CW
     bar_top_height: f32,        // Top bar height in pixels (for contain centering)
     bar_bottom_height: f32,     // Bottom bar height in pixels
+    _pad0: f32,                 // pad to vec4 alignment for letterbox_color
+    _pad1: f32,
+    letterbox_color: vec4<f32>, // RGBA — only used by the blur pass; declared here so the struct matches
 }
 
 @group(0) @binding(2)

src/app/video_shader_blur.wgsl

@@ -21,6 +21,9 @@ struct ViewportUniform {
     rotation: u32,              // Sensor rotation: 0=None, 1=90CW, 2=180, 3=270CW
     bar_top_height: f32,        // Top bar height in pixels
     bar_bottom_height: f32,     // Bottom bar height in pixels
+    _pad0: f32,                 // pad to vec4 alignment for letterbox_color
+    _pad1: f32,
+    letterbox_color: vec4<f32>, // RGBA fill for letterbox in blur pass (alpha unused)
 }
 
 @group(0) @binding(2)
@@ -117,10 +120,14 @@ fn fs_main(in: VertexOutput) -> @location(0) vec4<f32> {
         tex_coords = (tex_coords - pivot) * scale + vec2<f32>(0.5, 0.5);
     }
 
-    // Discard letterbox before the crop remap — see video_shader.wgsl for the
-    // rationale (post-remap check can falsely keep fragments inside the crop).
+    // For the blur backdrop, paint letterbox with the theme's background
+    // color (opaque) instead of discarding to transparent — the previous
+    // discard let the COSMIC window background show through in Contain /
+    // Fit mode. Return *before* the crop remap so we can short-circuit;
+    // the regular post-remap letterbox check is unnecessary here because
+    // anything out of [0,1] is letterbox by definition.
     if (tex_coords.x < 0.0 || tex_coords.x > 1.0 || tex_coords.y < 0.0 || tex_coords.y > 1.0) {
-        return vec4<f32>(0.0, 0.0, 0.0, 0.0);
+        return vec4<f32>(viewport.letterbox_color.rgb, 1.0);
     }
 
     // Apply the blended crop remap

src/app/video_shader_preblur.wgsl

@@ -31,6 +31,9 @@ struct ViewportUniform {
     rotation: u32,
     bar_top_height: f32,
     bar_bottom_height: f32,
+    _pad0: f32,
+    _pad1: f32,
+    letterbox_color: vec4<f32>, // unused here; struct must match the shared ViewportUniform
 }
 
 @group(0) @binding(2)

src/app/video_widget.rs

@@ -81,6 +81,10 @@ pub struct VideoWidgetConfig {
     /// Bottom UI bar height in pixels — matches the actual UI footprint
     /// (capture button + bottom bar + optional zoom row).
     pub bar_bottom_px: f32,
+    /// Theme background color (sRGB straight, RGBA). Used by the blur shader
+    /// to fill the letterbox in Contain / Fit mode instead of returning
+    /// transparent — otherwise the COSMIC window background leaks through.
+    pub letterbox_color: [f32; 4],
 }
 
 /// Video widget that renders camera frames using a custom GPU primitive
@@ -114,6 +118,7 @@ impl VideoWidget {
         primitive.rotation = config.rotation;
         primitive.crop_uv = config.crop_uv;
         primitive.zoom_level = config.zoom_level;
+        primitive.letterbox_color = config.letterbox_color;
 
         // Calculate aspect ratio from frame dimensions, adjusted for crop and rotation
         // For 90° and 270° rotations, swap width and height