[user textures] switch WHITE_UV to (0,0) and require clamped sampling

egui/src/paint/fonts.rs

@@ -87,20 +87,16 @@ impl Fonts {
 
         let mut atlas = TextureAtlas::new(512, 16); // TODO: better default?
 
-        // Make the top left four pixels fully white:
         {
-            let pos = atlas.allocate((2, 2));
+            // Make the top left pixel fully white:
+            let pos = atlas.allocate((1, 1));
             assert_eq!(pos, (0, 0));
-            let tex = atlas.texture_mut();
+            atlas.texture_mut()[pos] = 255;
-            tex[(0, 0)] = 255;
-            tex[(0, 1)] = 255;
-            tex[(1, 0)] = 255;
-            tex[(1, 1)] = 255;
         }
 
         let atlas = Arc::new(Mutex::new(atlas));
 
-        // TODO: figure out a way to make the wasm smaller despite including a font. Zip it?
+        // TODO: figure out a way to make the WASM smaller despite including a font. Zip it?
         let monospace_typeface_data = include_bytes!("../../fonts/ProggyClean.ttf"); // Use 13 for this. NOTHING ELSE.
 
         // let monospace_typeface_data = include_bytes!("../../fonts/Roboto-Regular.ttf");

egui/src/paint/tessellator.rs

@@ -15,7 +15,10 @@ use {
 };
 
 /// The UV coordinate of a white region of the texture mesh.
-pub const WHITE_UV: (u16, u16) = (1, 1);
+/// The default Egui texture has the top-left corner pixel fully white.
+/// You need need use a clamping texture sampler for this to work
+/// (so it doesn't do bilinear blending with bottom right corner).
+pub const WHITE_UV: (u16, u16) = (0, 0);
 
 /// The vertex type.
 ///
@@ -26,8 +29,11 @@ pub struct Vertex {
     /// Logical pixel coordinates (points).
     /// (0,0) is the top left corner of the screen.
     pub pos: Pos2, // 64 bit
-    /// Texel coordinates in the texture
+
+    /// Texel coordinates in the texture.
+    /// (0, 0) is the top left corner of the texture.
     pub uv: (u16, u16), // 32 bit
+
     /// sRGBA with premultiplied alpha
     pub color: Srgba, // 32 bit
 }

egui_glium/src/painter.rs

@@ -6,7 +6,10 @@ use {
         paint::{PaintJobs, Triangles},
         Rect,
     },
-    glium::{implement_vertex, index::PrimitiveType, program, texture, uniform, Frame, Surface},
+    glium::{
+        implement_vertex, index::PrimitiveType, program, texture, uniform,
+        uniforms::SamplerWrapFunction, Frame, Surface,
+    },
 };
 
 pub struct Painter {
@@ -108,7 +111,7 @@ impl Painter {
 
                         void main() {
                             // glium expects linear rgba
-                            gl_FragColor = v_rgba * texture2D`(u_sampler, v_tc).r;
+                            gl_FragColor = v_rgba * texture2D(u_sampler, v_tc).r;
                         }
                     ",
             },
@@ -255,7 +258,7 @@ impl Painter {
         let uniforms = uniform! {
             u_screen_size: [width_points, height_points],
             u_tex_size: [texture.width as f32, texture.height as f32],
-            u_sampler: &self.texture,
+            u_sampler: self.texture.sampled().wrap_function(SamplerWrapFunction::Clamp),
         };
 
         // Egui outputs colors with premultiplied alpha: