Use fast border algorithm, fix freezes

alvr/client_core/src/graphics/lobby.rs

@@ -1,6 +1,6 @@
 use super::{GraphicsContext, SDR_FORMAT};
 use alvr_common::{
-    glam::{Mat4, Quat, UVec2, Vec3, Vec4},
+    glam::{IVec2, Mat4, Quat, UVec2, Vec3, Vec4},
     Fov, Pose,
 };
 use glyph_brush_layout::{
@@ -25,16 +25,17 @@ const HUD_SIDE: f32 = 3.5;
 const HUD_TEXTURE_SIDE: usize = 1024;
 const FONT_SIZE: f32 = 50.0;
 
-const OPACITY_KERNEL_SIDE: usize = 7;
-const OPACITY_BORDER_KERNEL: [f32; OPACITY_KERNEL_SIDE * OPACITY_KERNEL_SIDE] = [
-    0.0, 0.0, 1.0, 1.0, 1.0, 0.0, 0.0, //
-    0.0, 1.0, 1.0, 1.0, 1.0, 1.0, 0.0, //
-    1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, //
-    1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, //
-    1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, //
-    0.0, 1.0, 1.0, 1.0, 1.0, 1.0, 0.0, //
-    0.0, 0.0, 1.0, 1.0, 1.0, 0.0, 0.0, //
+const FAST_BORDER_OFFSETS: [IVec2; 8] = [
+    IVec2::new(0, -3),
+    IVec2::new(2, -2),
+    IVec2::new(3, 0),
+    IVec2::new(2, 2),
+    IVec2::new(0, 3),
+    IVec2::new(-2, 2),
+    IVec2::new(-3, 0),
+    IVec2::new(-2, -2),
 ];
+const MAX_BORDER_OFFSET: i32 = 3;
 
 const HAND_SKELETON_BONES: [(usize, usize); 19] = [
     // Thumb
@@ -314,51 +315,35 @@ impl LobbyRenderer {
 
         let mut buffer = vec![0; HUD_TEXTURE_SIDE * HUD_TEXTURE_SIDE * 4];
 
-        // Render characters
         for section_glyph in section_glyphs {
             if let Some(outlined) = scaled_font.outline_glyph(section_glyph.glyph) {
                 let bounds = outlined.px_bounds();
+
                 outlined.draw(|x, y, alpha| {
-                    let x = x as usize + bounds.min.x as usize;
-                    let y = y as usize + bounds.min.y as usize;
-                    if x < HUD_TEXTURE_SIDE && y < HUD_TEXTURE_SIDE {
-                        let coord = (y * HUD_TEXTURE_SIDE + x) * 4;
+                    let x = x as i32 + bounds.min.x as i32;
+                    let y = y as i32 + bounds.min.y as i32;
+
+                    if x >= MAX_BORDER_OFFSET
+                        && y >= MAX_BORDER_OFFSET
+                        && x < HUD_TEXTURE_SIDE as i32 - MAX_BORDER_OFFSET
+                        && y < HUD_TEXTURE_SIDE as i32 - MAX_BORDER_OFFSET
+                    {
+                        let coord = (y as usize * HUD_TEXTURE_SIDE + x as usize) * 4;
                         let value = (alpha * 255.0) as u8;
 
                         buffer[coord] = value;
                         buffer[coord + 1] = value;
                         buffer[coord + 2] = value;
-                    }
-                });
-            }
-        }
 
-        // Render opacity
-        const KERNEL_HALF_SIDE: i32 = OPACITY_KERNEL_SIDE as i32 / 2;
-        for cy in 0..HUD_TEXTURE_SIDE as i32 {
-            for cx in 0..HUD_TEXTURE_SIDE as i32 {
-                let mut max_opacity = 0;
-                for off_y in 0..OPACITY_KERNEL_SIDE as i32 {
-                    for off_x in 0..OPACITY_KERNEL_SIDE as i32 {
-                        let tex_coord = ((cy + off_y - KERNEL_HALF_SIDE) * HUD_TEXTURE_SIDE as i32
-                            + (cx + off_x - KERNEL_HALF_SIDE))
-                            * 4;
-                        if tex_coord >= 0 && tex_coord < buffer.len() as i32 {
-                            // copy opacity from red channel
-                            let kernel_coord =
-                                off_y as usize * OPACITY_KERNEL_SIDE + off_x as usize;
-                            max_opacity = u8::max(
-                                (buffer[tex_coord as usize] as f32
-                                    * OPACITY_BORDER_KERNEL[kernel_coord])
-                                    as u8,
-                                max_opacity,
-                            );
+                        // Render opacity with border
+                        for offset in &FAST_BORDER_OFFSETS {
+                            let coord = ((y + offset.y) as usize * HUD_TEXTURE_SIDE
+                                + (x + offset.x) as usize)
+                                * 4;
+                            buffer[coord + 3] = u8::max(buffer[coord + 3], value);
                         }
                     }
-                }
-
-                let coord = (cy as usize * HUD_TEXTURE_SIDE + cx as usize) * 4;
-                buffer[coord as usize + 3] = max_opacity;
+                });
             }
         }