Add clipping back

examples/hello-world.rs

@@ -1,5 +1,5 @@
 use cosmic_text::{Attrs, Buffer, Color, Family, FontSystem, Metrics, SwashCache};
-use glyphon::{Resolution, TextAtlas, TextRenderer};
+use glyphon::{Resolution, TextArea, TextAtlas, TextBounds, TextRenderer};
 use wgpu::{
     Backends, CommandEncoderDescriptor, CompositeAlphaMode, DeviceDescriptor, Features, Instance,
     Limits, LoadOp, Operations, PresentMode, RenderPassColorAttachment, RenderPassDescriptor,
@@ -74,7 +74,7 @@ async fn run() {
     );
     buffer.set_size((width as f64 * scale_factor) as i32, (height as f64) as i32);
     buffer.set_text(
-        include_str!("./emoji.txt"),
+        include_str!("./emoji-zjw.txt"),
         Attrs::new().monospaced(true).family(Family::Monospace),
     );
     buffer.shape_until_scroll();
@@ -103,7 +103,15 @@ async fn run() {
                             width: config.width,
                             height: config.height,
                         },
-                        &buffer,
+                        &[TextArea {
+                            buffer: &buffer,
+                            bounds: TextBounds {
+                                left: 10,
+                                top: 10,
+                                right: 500,
+                                bottom: 50,
+                            },
+                        }],
                         Color::rgb(255, 255, 255),
                         &mut cache,
                     )

src/lib.rs

@@ -1,5 +1,3 @@
-use etagere::AllocId;
-
 mod error;
 mod recently_used;
 mod text_atlas;
@@ -12,6 +10,7 @@ use text_render::ContentType;
 pub use text_render::TextRenderer;
 
 pub use cosmic_text;
+use etagere::AllocId;
 
 pub(crate) enum GpuCacheStatus {
     InAtlas {
@@ -58,11 +57,35 @@ pub(crate) struct Params {
     _pad: [u32; 2],
 }
 
-/// Controls the overflow behavior of any glyphs that are outside of the layout bounds.
-pub enum TextOverflow {
-    /// Glyphs can overflow the bounds.
-    Overflow,
-    /// Hide any glyphs outside the bounds. If a glyph is partially outside the bounds, it will be
-    /// clipped to the bounds.
-    Hide,
+/// Controls the visible area of the text. Any text outside of the visible area will be clipped.
+#[derive(Clone, Copy, Debug, Eq, PartialEq)]
+pub struct TextBounds {
+    /// The position of the left edge of the visible area.
+    pub left: i32,
+    /// The position of the top edge of the visible area.
+    pub top: i32,
+    /// The position of the right edge of the visible area.
+    pub right: i32,
+    /// The position of the bottom edge of the visible area.
+    pub bottom: i32,
+}
+
+/// The default visible area doesn't clip any text.
+impl Default for TextBounds {
+    fn default() -> Self {
+        Self {
+            left: i32::MIN,
+            top: i32::MIN,
+            right: i32::MAX,
+            bottom: i32::MAX,
+        }
+    }
+}
+
+/// A text area containing text to be rendered along with its overflow behavior.
+pub struct TextArea<'a> {
+    /// The buffer containing the text to be rendered.
+    pub buffer: &'a cosmic_text::Buffer<'a>,
+    /// The bounds of the text area.
+    pub bounds: TextBounds,
 }

src/text_render.rs

@@ -1,6 +1,6 @@
 use crate::{
     GlyphDetails, GlyphToRender, GpuCacheStatus, Params, PrepareError, RenderError, Resolution,
-    TextAtlas, TextOverflow,
+    TextArea, TextAtlas,
 };
 use cosmic_text::{CacheKey, Color, SwashCache, SwashContent};
 use std::{collections::HashSet, iter, mem::size_of, num::NonZeroU32, slice};
@@ -53,14 +53,14 @@ impl TextRenderer {
         }
     }
 
-    /// Prepares all of the provided layouts for rendering.
+    /// Prepares all of the provided text areas for rendering.
     pub fn prepare<'a>(
         &mut self,
         device: &Device,
         queue: &Queue,
         atlas: &mut TextAtlas,
         screen_resolution: Resolution,
-        buffer: &cosmic_text::Buffer<'a>,
+        text_areas: &[TextArea<'a>],
         default_color: Color,
         cache: &mut SwashCache,
     ) -> Result<(), PrepareError> {
@@ -97,10 +97,8 @@ impl TextRenderer {
 
         self.glyphs_in_use.clear();
 
-        let mut buffers = [(buffer, TextOverflow::Hide)];
-
-        for (buffer, _) in buffers.iter_mut() {
-            for run in buffer.layout_runs() {
+        for text_area in text_areas.iter() {
+            for run in text_area.buffer.layout_runs() {
                 for glyph in run.glyphs.iter() {
                     self.glyphs_in_use.insert(glyph.cache_key);
 
@@ -240,15 +238,10 @@ impl TextRenderer {
         let mut glyph_indices: Vec<u32> = Vec::new();
         let mut glyphs_added = 0;
 
-        for (buffer, overflow) in buffers.iter() {
+        for text_area in text_areas.iter() {
             // Note: subpixel positioning is not currently handled, so we always truncate down to
-            // the nearest pixel.
-            let bounds_min_x = i32::MIN;
-            let bounds_max_x = i32::MAX;
-            let bounds_min_y = i32::MIN;
-            let bounds_max_y = i32::MAX;
-
-            for run in buffer.layout_runs() {
+            // the nearest pixel whenever necessary.
+            for run in text_area.buffer.layout_runs() {
                 let line_y = run.line_y;
 
                 for glyph in run.glyphs.iter() {
@@ -270,9 +263,11 @@ impl TextRenderer {
                     let mut width = details.width as i32;
                     let mut height = details.height as i32;
 
-                    match overflow {
-                        TextOverflow::Overflow => {}
-                        TextOverflow::Hide => {
+                    let bounds_min_x = text_area.bounds.left.max(0);
+                    let bounds_min_y = text_area.bounds.top.max(0);
+                    let bounds_max_x = text_area.bounds.right.min(screen_resolution.width as i32);
+                    let bounds_max_y = text_area.bounds.bottom.min(screen_resolution.height as i32);
+
                     // Starts beyond right edge or ends beyond left edge
                     let max_x = x + width;
                     if x > bounds_max_x || max_x < bounds_min_x {
@@ -312,8 +307,6 @@ impl TextRenderer {
                     if y + height > bounds_max_y {
                         height = bounds_max_y - y;
                     }
-                        }
-                    }
 
                     glyph_vertices.extend(
                         iter::repeat(GlyphToRender {