Use geomtry shader to render text

space-crush-app/resources/shader/text/geom.glsl

@@ -0,0 +1,38 @@
+#version 450 core
+
+#pragma include ./shared.glsl
+
+in VertexData vertexData[];
+
+layout (points) in;
+layout (triangle_strip, max_vertices = 4) out;
+
+layout (location = 2) uniform vec2 uOffset;
+
+out FragmentData fragmentData;
+
+void main() {
+    VertexData d = vertexData[0];
+
+    gl_Position            = vec4(vec2(d.posMin.x, d.posMax.y), 0.0, 1.0);
+    fragmentData.texCoords =      vec2(d.texMin.x, d.texMax.y);
+    fragmentData.color     =           d.color;
+    EmitVertex();
+
+    gl_Position            = vec4(vec2(d.posMin.x, d.posMin.y), 0.0, 1.0);
+    fragmentData.texCoords =      vec2(d.texMin.x, d.texMin.y);
+    fragmentData.color     =           d.color;
+    EmitVertex();
+
+    gl_Position            = vec4(vec2(d.posMax.x, d.posMax.y), 0.0, 1.0);
+    fragmentData.texCoords =      vec2(d.texMax.x, d.texMax.y);
+    fragmentData.color     =           d.color;
+    EmitVertex();
+
+    gl_Position            = vec4(vec2(d.posMax.x, d.posMin.y), 0.0, 1.0);
+    fragmentData.texCoords =      vec2(d.texMax.x, d.texMin.y);
+    fragmentData.color     =           d.color;
+    EmitVertex();
+
+    EndPrimitive();
+}

space-crush-app/resources/shader/text/shared.glsl

@@ -2,3 +2,11 @@ struct FragmentData {
     vec2 texCoords;
     vec4 color;
 };
+
+struct VertexData {
+    vec2 posMin;
+    vec2 posMax;
+    vec2 texMin;
+    vec2 texMax;
+    vec4 color;
+};

space-crush-app/resources/shader/text/vert.glsl

@@ -11,34 +11,9 @@ layout (location = 4) in vec4 inColor;
 
 layout (location = 2) uniform vec2 uOffset;
 
-out FragmentData fragmentData;
+out VertexData vertexData;
 
 void main() {
-    vec2 position = vec2(0.0);
-    vec2 texCoords = vec2(0.0);
-
-    switch (gl_VertexID) {
-        case 0:
-            position = vec2(inPosMin.x, inPosMax.y);
-            texCoords = vec2(inTexMin.x, inTexMax.y);
-            break;
-
-        case 1:
-            position = vec2(inPosMin.x, inPosMin.y);
-            texCoords = vec2(inTexMin.x, inTexMin.y);
-            break;
-
-        case 2:
-            position = vec2(inPosMax.x, inPosMax.y);
-            texCoords = vec2(inTexMax.x, inTexMax.y);
-            break;
-
-        case 3:
-            position = vec2(inPosMax.x, inPosMin.y);
-            texCoords = vec2(inTexMax.x, inTexMin.y);
-            break;
-    }
-
     mat4 ortho = mat4(
         vec4(2.0 / uCamera.size.x, 0.0, 0.0, 0.0),
         vec4(0.0, -2.0 / uCamera.size.y, 0.0, 0.0),
@@ -46,8 +21,9 @@ void main() {
         vec4(-1.0, 1.0, 1.0, 1.0)
     );
 
-    gl_Position = ortho * vec4(position + uOffset, 0.0, 1.0);
-
-    fragmentData.texCoords = texCoords;
-    fragmentData.color = inColor;
+    vertexData.posMin = (ortho * vec4(inPosMin + uOffset, 0.0, 1.0)).xy;
+    vertexData.posMax = (ortho * vec4(inPosMax + uOffset, 0.0, 1.0)).xy;
+    vertexData.texMin = inTexMin;
+    vertexData.texMax = inTexMax;
+    vertexData.color = inColor;
 }

space-crush-app/src/misc/text.rs

@@ -48,6 +48,7 @@ impl TextManager {
         let vfs = world.resource::<Vfs>()?.deref().clone();
         let program = world.load_program(vec![
             (Type::Vertex, "resources/shader/text/vert.glsl"),
+            (Type::Geometry, "resources/shader/text/geom.glsl"),
             (Type::Fragment, "resources/shader/text/frag.glsl"),
         ])?;
         let program = Rc::new(program);
@@ -595,15 +596,10 @@ impl Text {
         let array = VertexArray::builder()
             .bind_buffer(buffer)
             .vertex_attrib_pointer(0, 2, DataType::Float, false, STRIDE, OFFSET_POS_MIN)?
-            .vertex_attrib_divisor(1)?
             .vertex_attrib_pointer(1, 2, DataType::Float, false, STRIDE, OFFSET_POS_MAX)?
-            .vertex_attrib_divisor(1)?
             .vertex_attrib_pointer(2, 2, DataType::Float, false, STRIDE, OFFSET_TEX_MIN)?
-            .vertex_attrib_divisor(1)?
             .vertex_attrib_pointer(3, 2, DataType::Float, false, STRIDE, OFFSET_TEX_MAX)?
-            .vertex_attrib_divisor(1)?
             .vertex_attrib_pointer(4, 4, DataType::Float, false, STRIDE, OFFSET_COLOR)?
-            .vertex_attrib_divisor(1)?
             .build()?;
 
         let cache = cache.clone();
@@ -647,7 +643,9 @@ impl Text {
             .uniform(2, Uniform::Vector2f(pos))
             .warn("Unable to update text offset");
 
-        gl::draw_arrays_instanced(gl::TRIANGLE_STRIP, 0, 4, inner.vertex_count as _);
+        // gl::draw_arrays(gl::POINTS, 0, inner.vertex_count as _);
+        gl::draw_arrays(gl::POINTS, 0, inner.vertex_count as _);
+        // gl::draw_arrays_instanced(gl::POINTS, 0, 1, inner.vertex_count as _);
     }
 
     pub fn update<S>(&mut self, mut index: usize, text: S) -> Result<&Self, Error>