From fd8a2cc15b9c4d49afeed12879d05b8457c95bd9 Mon Sep 17 00:00:00 2001
From: Andrew Hamilton <and_hamilton@yahoo.com>
Date: Thu, 23 Jul 2026 06:20:35 +1000
Subject: [PATCH] Cap atlas size to device max_texture_dimension_2d

RPi5 GPU limits max texture dimension to 2048, but atlas was hardcoded
to 2560. Now clamps to device.limits().max_texture_dimension_2d.
---
 src/atlas.rs    | 19 +++++++++++++------
 src/renderer.rs |  8 ++++----
 2 files changed, 17 insertions(+), 10 deletions(-)

diff --git a/src/atlas.rs b/src/atlas.rs
index f427e64..5b3bdaa 100644
--- a/src/atlas.rs
+++ b/src/atlas.rs
@@ -14,6 +14,7 @@ pub(crate) struct GlyphAtlas {
     scale: f32,
     cell_width: u32,
     cell_height: u32,
+    atlas_size: u32,
     rasterizer: GlyphRasterizer,
     next_slot: u32,
     glyph_map: HashMap<(char, u8), u32>,
@@ -30,10 +31,11 @@ impl GlyphAtlas {
         color_font_path: Option<&str>,
     ) -> Self {
         let color_font = color_font_path.map(font::load_color_font);
+        let atlas_size = ATLAS_SIZE.min(device.limits().max_texture_dimension_2d);
 
         let size = wgpu::Extent3d {
-            width: ATLAS_SIZE,
-            height: ATLAS_SIZE,
+            width: atlas_size,
+            height: atlas_size,
             depth_or_array_layers: 1,
         };
         let texture = device.create_texture(&wgpu::TextureDescriptor {
@@ -77,6 +79,7 @@ impl GlyphAtlas {
             scale,
             cell_width,
             cell_height,
+            atlas_size,
             rasterizer: GlyphRasterizer::new(),
             next_slot: 1,
             glyph_map: HashMap::new(),
@@ -95,16 +98,20 @@ impl GlyphAtlas {
         self.cell_height
     }
 
+    pub fn atlas_size(&self) -> u32 {
+        self.atlas_size
+    }
+
     pub fn scale(&self) -> f32 {
         self.scale
     }
 
     pub fn atlas_cols(&self) -> u32 {
-        ATLAS_SIZE / self.cell_width
+        self.atlas_size / self.cell_width
     }
 
     pub fn atlas_rows(&self) -> u32 {
-        ATLAS_SIZE / self.cell_height
+        self.atlas_size / self.cell_height
     }
 
     pub fn max_glyphs(&self) -> u32 {
@@ -119,8 +126,8 @@ impl GlyphAtlas {
         self.cell_height = h;
 
         let size = wgpu::Extent3d {
-            width: ATLAS_SIZE,
-            height: ATLAS_SIZE,
+            width: self.atlas_size,
+            height: self.atlas_size,
             depth_or_array_layers: 1,
         };
         self.texture = device.create_texture(&wgpu::TextureDescriptor {
diff --git a/src/renderer.rs b/src/renderer.rs
index 932de33..a3b4ebf 100644
--- a/src/renderer.rs
+++ b/src/renderer.rs
@@ -225,7 +225,7 @@ pub fn start(
         })
     }
 
-    write_uniform(&queue, &uniform_buffer, cols, rows, cell_w as f32, cell_h as f32, fb_w, fb_h, atlas.atlas_cols(), atlas.atlas_rows(), crate::atlas::ATLAS_SIZE as f32);
+    write_uniform(&queue, &uniform_buffer, cols, rows, cell_w as f32, cell_h as f32, fb_w, fb_h, atlas.atlas_cols(), atlas.atlas_rows(), atlas.atlas_size() as f32);
 
     // ----- Sampler -----
     let sampler = device.create_sampler(&wgpu::SamplerDescriptor {
@@ -357,7 +357,7 @@ pub fn start(
                         let a_rows = atlas.atlas_rows();
                         write_uniform(&queue, &uniform_buffer, cols, rows,
                             atlas.cell_width() as f32, atlas.cell_height() as f32,
-                            fb_w, fb_h, a_cols, a_rows, crate::atlas::ATLAS_SIZE as f32);
+                            fb_w, fb_h, a_cols, a_rows, atlas.atlas_size() as f32);
                         needs_render.store(true, Ordering::Release);
                     } else {
                         let s: Option<String> =
@@ -445,7 +445,7 @@ pub fn start(
                         let a_rows = atlas.atlas_rows();
                         write_uniform(&queue, &uniform_buffer, cols, rows,
                             atlas.cell_width() as f32, atlas.cell_height() as f32,
-                            fbw, fbh, a_cols, a_rows, crate::atlas::ATLAS_SIZE as f32);
+                            fbw, fbh, a_cols, a_rows, atlas.atlas_size() as f32);
                     }
                 }
                 _ => {}
@@ -493,7 +493,7 @@ pub fn start(
             let a_rows = atlas.atlas_rows();
             write_uniform(&queue, &uniform_buffer, cols, rows,
                 atlas.cell_width() as f32, atlas.cell_height() as f32,
-                fb_w, fb_h, a_cols, a_rows, crate::atlas::ATLAS_SIZE as f32);
+                fb_w, fb_h, a_cols, a_rows, atlas.atlas_size() as f32);
         }
 
         if needs_render.load(Ordering::Acquire) {