🎉 Improve text inner stroke rendering

render-wasm/src/render.rs

@@ -26,7 +26,7 @@ use crate::error::{Error, Result};
 use crate::performance;
 use crate::shapes::{
     all_with_ancestors, radius_to_sigma, Blur, BlurType, Corners, Fill, Shadow, Shape, SolidColor,
-    Stroke, Type,
+    Stroke, StrokeKind, Type,
 };
 use crate::state::{ShapesPoolMutRef, ShapesPoolRef};
 use crate::tiles::{self, PendingTiles, TileRect};
@@ -1030,6 +1030,8 @@ impl RenderState {
                 let text_stroke_blur_outset =
                     Stroke::max_bounds_width(shape.visible_strokes(), false);
                 let mut paragraph_builders = text_content.paragraph_builder_group_from_text(None);
+                let stroke_kinds: Vec<StrokeKind> =
+                    shape.visible_strokes().rev().map(|s| s.kind).collect();
                 let (mut stroke_paragraphs_list, stroke_opacities): (Vec<_>, Vec<_>) = shape
                     .visible_strokes()
                     .rev()
@@ -1038,7 +1040,6 @@ impl RenderState {
                             &text_content,
                             stroke,
                             &shape.selrect(),
-                            count_inner_strokes,
                             None,
                         )
                     })
@@ -1057,22 +1058,41 @@ impl RenderState {
                         None,
                     )?;
 
-                    for (stroke_paragraphs, layer_opacity) in stroke_paragraphs_list
+                    for (i, (stroke_paragraphs, layer_opacity)) in stroke_paragraphs_list
                         .iter_mut()
                         .zip(stroke_opacities.iter())
+                        .enumerate()
                     {
-                        text::render_with_bounds_outset(
-                            Some(self),
-                            None,
-                            &shape,
-                            stroke_paragraphs,
-                            Some(strokes_surface_id),
-                            None,
-                            None,
-                            text_stroke_blur_outset,
-                            None,
-                            *layer_opacity,
-                        )?;
+                        if stroke_kinds[i] == StrokeKind::Inner {
+                            let mut mask_builders = text_content.paragraph_builder_group_opaque();
+                            let mut fill_builders =
+                                text_content.paragraph_builder_group_from_text(None);
+                            text::render_inner_stroke(
+                                Some(self),
+                                None,
+                                &shape,
+                                &mut mask_builders,
+                                stroke_paragraphs,
+                                &mut fill_builders,
+                                Some(strokes_surface_id),
+                                None,
+                                text_stroke_blur_outset,
+                                *layer_opacity,
+                            )?;
+                        } else {
+                            text::render_with_bounds_outset(
+                                Some(self),
+                                None,
+                                &shape,
+                                stroke_paragraphs,
+                                Some(strokes_surface_id),
+                                None,
+                                None,
+                                text_stroke_blur_outset,
+                                None,
+                                *layer_opacity,
+                            )?;
+                        }
                     }
                 } else {
                     let mut drop_shadows = shape.drop_shadow_paints();
@@ -1096,7 +1116,6 @@ impl RenderState {
                                 &text_content,
                                 stroke,
                                 &shape.selrect(),
-                                count_inner_strokes,
                                 Some(true),
                             )
                         })
@@ -1126,6 +1145,8 @@ impl RenderState {
                                 text_drop_shadows_surface_id.into(),
                                 &parent_shadows,
                                 &blur_filter,
+                                &stroke_kinds,
+                                &text_content,
                             )?;
                         }
                     } else {
@@ -1168,25 +1189,47 @@ impl RenderState {
                             text_drop_shadows_surface_id.into(),
                             &drop_shadows,
                             &blur_filter,
+                            &stroke_kinds,
+                            &text_content,
                         )?;
 
                         // 4. Stroke fills
-                        for (stroke_paragraphs, layer_opacity) in stroke_paragraphs_list
+                        for (i, (stroke_paragraphs, layer_opacity)) in stroke_paragraphs_list
                             .iter_mut()
                             .zip(stroke_opacities.iter())
+                            .enumerate()
                         {
-                            text::render_with_bounds_outset(
-                                Some(self),
-                                None,
-                                &shape,
-                                stroke_paragraphs,
-                                Some(strokes_surface_id),
-                                None,
-                                blur_filter.as_ref(),
-                                text_stroke_blur_outset,
-                                None,
-                                *layer_opacity,
-                            )?;
+                            if stroke_kinds[i] == StrokeKind::Inner {
+                                let mut mask_builders =
+                                    text_content.paragraph_builder_group_opaque();
+                                let mut fill_builders =
+                                    text_content.paragraph_builder_group_from_text(None);
+                                text::render_inner_stroke(
+                                    Some(self),
+                                    None,
+                                    &shape,
+                                    &mut mask_builders,
+                                    stroke_paragraphs,
+                                    &mut fill_builders,
+                                    Some(strokes_surface_id),
+                                    blur_filter.as_ref(),
+                                    text_stroke_blur_outset,
+                                    *layer_opacity,
+                                )?;
+                            } else {
+                                text::render_with_bounds_outset(
+                                    Some(self),
+                                    None,
+                                    &shape,
+                                    stroke_paragraphs,
+                                    Some(strokes_surface_id),
+                                    None,
+                                    blur_filter.as_ref(),
+                                    text_stroke_blur_outset,
+                                    None,
+                                    *layer_opacity,
+                                )?;
+                            }
                         }
 
                         // 5. Stroke inner shadows
@@ -1198,6 +1241,8 @@ impl RenderState {
                             Some(innershadows_surface_id),
                             &inner_shadows,
                             &blur_filter,
+                            &stroke_kinds,
+                            &text_content,
                         )?;
 
                         // 6. Fill Inner shadows

render-wasm/src/render/shadows.rs

@@ -1,6 +1,6 @@
 use super::{RenderState, SurfaceId};
 use crate::render::strokes;
-use crate::shapes::{ParagraphBuilderGroup, Shadow, Shape, Stroke, Type};
+use crate::shapes::{ParagraphBuilderGroup, Shadow, Shape, Stroke, StrokeKind, TextContent, Type};
 use skia_safe::{canvas::SaveLayerRec, Paint, Path};
 
 use crate::error::Result;
@@ -127,6 +127,7 @@ fn render_shadow_paint(
     }
 }
 
+#[allow(clippy::too_many_arguments)]
 pub fn render_text_shadows(
     render_state: &mut RenderState,
     shape: &Shape,
@@ -135,6 +136,8 @@ pub fn render_text_shadows(
     surface_id: Option<SurfaceId>,
     shadows: &[Paint],
     blur_filter: &Option<skia_safe::ImageFilter>,
+    stroke_kinds: &[StrokeKind],
+    text_content: &TextContent,
 ) -> Result<()> {
     if stroke_paragraphs_group.is_empty() {
         return Ok(());
@@ -160,18 +163,35 @@ pub fn render_text_shadows(
             None,
         )?;
 
-        for stroke_paragraphs in stroke_paragraphs_group.iter_mut() {
-            text::render(
-                None,
-                Some(canvas),
-                shape,
-                stroke_paragraphs,
-                surface_id,
-                None,
-                blur_filter.as_ref(),
-                None,
-                None,
-            )?;
+        for (i, stroke_paragraphs) in stroke_paragraphs_group.iter_mut().enumerate() {
+            if i < stroke_kinds.len() && stroke_kinds[i] == StrokeKind::Inner {
+                let mut mask_builders = text_content.paragraph_builder_group_opaque();
+                let mut fill_builders = text_content.paragraph_builder_group_from_text(Some(true));
+                text::render_inner_stroke(
+                    None,
+                    Some(canvas),
+                    shape,
+                    &mut mask_builders,
+                    stroke_paragraphs,
+                    &mut fill_builders,
+                    surface_id,
+                    blur_filter.as_ref(),
+                    0.0,
+                    None,
+                )?;
+            } else {
+                text::render(
+                    None,
+                    Some(canvas),
+                    shape,
+                    stroke_paragraphs,
+                    surface_id,
+                    None,
+                    blur_filter.as_ref(),
+                    None,
+                    None,
+                )?;
+            }
         }
 
         canvas.restore();

render-wasm/src/render/text.rs

@@ -3,8 +3,8 @@ use crate::{
     error::Result,
     math::Rect,
     shapes::{
-        calculate_position_data, calculate_text_layout_data, merge_fills, set_paint_fill,
-        ParagraphBuilderGroup, Stroke, StrokeKind, TextContent,
+        calculate_position_data, calculate_text_layout_data, set_paint_fill, ParagraphBuilderGroup,
+        Stroke, StrokeKind, TextContent,
     },
     utils::{get_fallback_fonts, get_font_collection},
 };
@@ -19,7 +19,6 @@ pub fn stroke_paragraph_builder_group_from_text(
     text_content: &TextContent,
     stroke: &Stroke,
     bounds: &Rect,
-    count_inner_strokes: usize,
     use_shadow: Option<bool>,
 ) -> (Vec<ParagraphBuilderGroup>, Option<f32>) {
     let fallback_fonts = get_fallback_fonts();
@@ -33,14 +32,8 @@ pub fn stroke_paragraph_builder_group_from_text(
             std::collections::HashMap::new();
 
         for span in paragraph.children().iter() {
-            let text_paint: skia_safe::Handle<_> = merge_fills(span.fills(), *bounds);
-            let (stroke_paints, stroke_layer_opacity) = get_text_stroke_paints(
-                stroke,
-                bounds,
-                &text_paint,
-                count_inner_strokes,
-                remove_stroke_alpha,
-            );
+            let (stroke_paints, stroke_layer_opacity) =
+                get_text_stroke_paints(stroke, bounds, remove_stroke_alpha);
 
             if group_layer_opacity.is_none() {
                 group_layer_opacity = stroke_layer_opacity;
@@ -79,8 +72,6 @@ pub fn stroke_paragraph_builder_group_from_text(
 fn get_text_stroke_paints(
     stroke: &Stroke,
     bounds: &Rect,
-    text_paint: &Paint,
-    count_inner_strokes: usize,
     remove_stroke_alpha: bool,
 ) -> (Vec<Paint>, Option<f32>) {
     let mut paints = Vec::new();
@@ -104,56 +95,19 @@ fn get_text_stroke_paints(
 
     match stroke.kind {
         StrokeKind::Inner => {
-            let shader = text_paint.shader();
-            let mut is_opaque = true;
-
-            if let Some(shader) = shader {
-                is_opaque = shader.is_opaque();
-            }
-
-            if is_opaque && count_inner_strokes == 1 {
-                let mut paint = text_paint.clone();
-                paint.set_style(skia::PaintStyle::Fill);
-                paint.set_anti_alias(true);
-                paints.push(paint);
-
-                let mut paint = skia::Paint::default();
-                paint.set_style(skia::PaintStyle::Stroke);
-                paint.set_blend_mode(skia::BlendMode::SrcIn);
-                paint.set_anti_alias(true);
-                paint.set_stroke_width(stroke.width * 2.0);
-                fill_for_paint(&mut paint);
-                paints.push(paint);
-            } else {
-                let mut paint = skia::Paint::default();
-                if remove_stroke_alpha {
-                    paint.set_color(skia::Color::BLACK);
-                    paint.set_alpha(255);
-                } else {
-                    paint = text_paint.clone();
-                    if needs_opacity_layer {
-                        let opaque_fill = stroke.fill.with_full_opacity();
-                        set_paint_fill(&mut paint, &opaque_fill, bounds, false);
-                    } else {
-                        set_paint_fill(&mut paint, &stroke.fill, bounds, false);
-                    }
-                }
-
-                paint.set_style(skia::PaintStyle::Fill);
-                paint.set_anti_alias(false);
-                paints.push(paint);
-
-                let mut paint = skia::Paint::default();
-                let image_filter =
-                    skia_safe::image_filters::erode((stroke.width, stroke.width), None, None);
-
-                paint.set_image_filter(image_filter);
-                paint.set_anti_alias(false);
+            // Just the stroke paint — mask+SrcIn+DstOver layering is handled
+            // by render_inner_stroke_on_canvas.
+            let mut paint = skia::Paint::default();
+            paint.set_style(skia::PaintStyle::Stroke);
+            paint.set_anti_alias(true);
+            paint.set_stroke_width(stroke.width * 2.0);
+            if remove_stroke_alpha {
                 paint.set_color(skia::Color::BLACK);
                 paint.set_alpha(255);
-                paint.set_blend_mode(skia::BlendMode::DstOut);
-                paints.push(paint);
+            } else {
+                fill_for_paint(&mut paint);
             }
+            paints.push(paint);
         }
         StrokeKind::Center => {
             let mut paint = skia::Paint::default();
@@ -330,25 +284,16 @@ fn render_text_on_canvas(
     canvas.restore();
 }
 
-fn draw_text(
+/// Lays out and paints paragraph builders without any layer management.
+fn paint_text(
     canvas: &Canvas,
     shape: &Shape,
     paragraph_builder_groups: &mut [Vec<ParagraphBuilder>],
-    layer_opacity: Option<f32>,
 ) {
     let text_content = shape.get_text_content();
     let layout_info =
         calculate_text_layout_data(shape, text_content, paragraph_builder_groups, true);
 
-    if let Some(opacity) = layer_opacity {
-        let mut opacity_paint = Paint::default();
-        opacity_paint.set_alpha_f(opacity);
-        let layer_rec = SaveLayerRec::default().paint(&opacity_paint);
-        canvas.save_layer(&layer_rec);
-    } else {
-        canvas.save_layer(&SaveLayerRec::default());
-    }
-
     for para in &layout_info.paragraphs {
         para.paragraph.paint(canvas, (para.x, para.y));
         for deco in &para.decorations {
@@ -364,6 +309,178 @@ fn draw_text(
     }
 }
 
+fn draw_text(
+    canvas: &Canvas,
+    shape: &Shape,
+    paragraph_builder_groups: &mut [Vec<ParagraphBuilder>],
+    layer_opacity: Option<f32>,
+) {
+    if let Some(opacity) = layer_opacity {
+        let mut opacity_paint = Paint::default();
+        opacity_paint.set_alpha_f(opacity);
+        let layer_rec = SaveLayerRec::default().paint(&opacity_paint);
+        canvas.save_layer(&layer_rec);
+    } else {
+        canvas.save_layer(&SaveLayerRec::default());
+    }
+
+    paint_text(canvas, shape, paragraph_builder_groups);
+}
+
+/// Renders an inner stroke using mask + SrcIn + DstOver layer structure.
+///
+/// Layer structure:
+///   saveLayer()           — outer layer
+///     saveLayer()         — mask group (isolation)
+///       paint mask        — opaque fill as clip mask
+///       saveLayer(SrcIn)  — clips stroke to mask shape
+///         paint stroke
+///       restore
+///     restore
+///     saveLayer(DstOver)  — fill behind the stroke
+///       paint fill
+///     restore
+///   restore
+#[allow(clippy::too_many_arguments)]
+fn render_inner_stroke_on_canvas(
+    canvas: &Canvas,
+    shape: &Shape,
+    mask_builders: &mut [Vec<ParagraphBuilder>],
+    stroke_builders: &mut [Vec<ParagraphBuilder>],
+    fill_builders: &mut [Vec<ParagraphBuilder>],
+    blur: Option<&ImageFilter>,
+    layer_opacity: Option<f32>,
+) {
+    if let Some(blur_filter) = blur {
+        let mut blur_paint = Paint::default();
+        blur_paint.set_image_filter(blur_filter.clone());
+        canvas.save_layer(&SaveLayerRec::default().paint(&blur_paint));
+    }
+
+    // Opacity layer wraps the entire composition
+    if let Some(opacity) = layer_opacity {
+        let mut opacity_paint = Paint::default();
+        opacity_paint.set_alpha_f(opacity);
+        canvas.save_layer(&SaveLayerRec::default().paint(&opacity_paint));
+    }
+
+    // Outer layer
+    canvas.save_layer(&SaveLayerRec::default());
+
+    // Mask group layer (isolates mask from parent surface content)
+    canvas.save_layer(&SaveLayerRec::default());
+
+    // Draw opaque mask (full alpha text shape)
+    paint_text(canvas, shape, mask_builders);
+
+    // SrcIn layer — only keeps stroke pixels where mask has alpha
+    let mut src_in_paint = Paint::default();
+    src_in_paint.set_blend_mode(skia::BlendMode::SrcIn);
+    canvas.save_layer(&SaveLayerRec::default().paint(&src_in_paint));
+
+    // Draw stroke
+    paint_text(canvas, shape, stroke_builders);
+
+    canvas.restore(); // SrcIn layer
+    canvas.restore(); // mask group layer
+
+    // Fill with DstOver (behind the stroke result)
+    let mut dst_over_paint = Paint::default();
+    dst_over_paint.set_blend_mode(skia::BlendMode::DstOver);
+    canvas.save_layer(&SaveLayerRec::default().paint(&dst_over_paint));
+
+    paint_text(canvas, shape, fill_builders);
+
+    canvas.restore(); // DstOver layer
+    canvas.restore(); // outer layer
+
+    if layer_opacity.is_some() {
+        canvas.restore(); // opacity layer
+    }
+
+    if blur.is_some() {
+        canvas.restore(); // blur layer
+    }
+}
+
+/// Public API for rendering inner strokes with mask+SrcIn+DstOver approach.
+#[allow(clippy::too_many_arguments)]
+pub fn render_inner_stroke(
+    render_state: Option<&mut RenderState>,
+    canvas: Option<&Canvas>,
+    shape: &Shape,
+    mask_builders: &mut [Vec<ParagraphBuilder>],
+    stroke_builders: &mut [Vec<ParagraphBuilder>],
+    fill_builders: &mut [Vec<ParagraphBuilder>],
+    surface_id: Option<SurfaceId>,
+    blur: Option<&ImageFilter>,
+    stroke_bounds_outset: f32,
+    layer_opacity: Option<f32>,
+) -> Result<()> {
+    if let Some(render_state) = render_state {
+        let target_surface = surface_id.unwrap_or(SurfaceId::Fills);
+
+        if let Some(blur_filter) = blur {
+            let mut text_bounds = shape
+                .get_text_content()
+                .calculate_bounds(shape, false)
+                .to_rect();
+            if stroke_bounds_outset > 0.0 {
+                text_bounds.inset((-stroke_bounds_outset, -stroke_bounds_outset));
+            }
+            let bounds = blur_filter.compute_fast_bounds(text_bounds);
+            if bounds.is_finite() && bounds.width() > 0.0 && bounds.height() > 0.0 {
+                let blur_filter_clone = blur_filter.clone();
+                if filters::render_with_filter_surface(
+                    render_state,
+                    bounds,
+                    target_surface,
+                    |state, temp_surface| {
+                        let temp_canvas = state.surfaces.canvas(temp_surface);
+                        render_inner_stroke_on_canvas(
+                            temp_canvas,
+                            shape,
+                            mask_builders,
+                            stroke_builders,
+                            fill_builders,
+                            Some(&blur_filter_clone),
+                            layer_opacity,
+                        );
+                        Ok(())
+                    },
+                )? {
+                    return Ok(());
+                }
+            }
+        }
+
+        let canvas = render_state.surfaces.canvas_and_mark_dirty(target_surface);
+        render_inner_stroke_on_canvas(
+            canvas,
+            shape,
+            mask_builders,
+            stroke_builders,
+            fill_builders,
+            blur,
+            layer_opacity,
+        );
+        return Ok(());
+    }
+
+    if let Some(canvas) = canvas {
+        render_inner_stroke_on_canvas(
+            canvas,
+            shape,
+            mask_builders,
+            stroke_builders,
+            fill_builders,
+            blur,
+            layer_opacity,
+        );
+    }
+    Ok(())
+}
+
 fn draw_text_decorations(
     canvas: &Canvas,
     text_style: &TextStyle,

render-wasm/src/shapes/text.rs

@@ -605,6 +605,40 @@ impl TextContent {
         paragraph_group
     }
 
+    /// Creates paragraph builders with always-opaque paint (BLACK @ alpha 255).
+    /// Used as a clip mask for inner stroke rendering.
+    pub fn paragraph_builder_group_opaque(&self) -> Vec<ParagraphBuilderGroup> {
+        let fonts = get_font_collection();
+        let fallback_fonts = get_fallback_fonts();
+        let mut paragraph_group = Vec::new();
+
+        for paragraph in self.paragraphs() {
+            let paragraph_style = paragraph.paragraph_to_style();
+            let mut builder = ParagraphBuilder::new(&paragraph_style, fonts);
+            let mut has_text = false;
+            for span in paragraph.children() {
+                let text_style = span.to_style(
+                    &self.bounds(),
+                    fallback_fonts,
+                    true, // always opaque
+                    paragraph.line_height(),
+                );
+                let text: String = span.apply_text_transform();
+                if !text.is_empty() {
+                    has_text = true;
+                }
+                builder.push_style(&text_style);
+                builder.add_text(&text);
+            }
+            if !has_text {
+                builder.add_text(" ");
+            }
+            paragraph_group.push(vec![builder]);
+        }
+
+        paragraph_group
+    }
+
     /// Performs an Auto Width text layout.
     fn text_layout_auto_width(&self) -> TextContentLayoutResult {
         let mut paragraph_builders = self.paragraph_builder_group_from_text(None);
@@ -1094,6 +1128,7 @@ impl TextSpan {
         self.text = text;
     }
 
+    #[allow(dead_code)]
     pub fn fills(&self) -> &[shapes::Fill] {
         &self.fills
     }