From c2557116a8af6b4c8cb0af9edc12bd88ad4ad233 Mon Sep 17 00:00:00 2001
From: Zack Buhman <zack@buhman.org>
Date: Tue, 6 Jan 2026 22:15:24 -0600
Subject: [PATCH] font.fx: generate quad via geometry shader

---
 font.fx      | 44 +++++++++++++++++++++++++++++++++-----------
 src/main.cpp |  4 ++--
 2 files changed, 35 insertions(+), 13 deletions(-)

diff --git a/font.fx b/font.fx
index c618200..15828da 100644
--- a/font.fx
+++ b/font.fx
@@ -16,27 +16,49 @@ struct VS_INPUT
   float2 Pos : POSITION;
 };
 
-struct PS_INPUT
+struct GSPS_INPUT
 {
   float4 Pos : SV_POSITION;
   float2 Tex : TEXCOORD0;
 };
 
-PS_INPUT VS(VS_INPUT input)
+GSPS_INPUT VS(VS_INPUT input)
 {
-  PS_INPUT output = (PS_INPUT)0;
+  GSPS_INPUT output = (GSPS_INPUT)0;
 
-  float2 Pos = input.Pos * vGlyphScale + vPosition;
-  Pos = Pos * vInvScreenSize + float2(-1, 1);
-  output.Pos = float4(Pos.xy, 0, 1);
+  output.Pos = float4(0, 0, 0, 0);
+  output.Tex = float2(0, 0);
 
-  float2 Tex = float2(input.Pos.x, -input.Pos.y);
-
-  output.Tex = (Tex + vCharCoord) * vTexScale;
   return output;
 }
 
-float4 PS(PS_INPUT input) : SV_Target
+static const float2 vertices[] = {
+  float2( 0.0f,  0.0f), // -- top right
+  float2( 1.0f,  0.0f), // -- top left
+  float2( 0.0f, -1.0f), // -- bottom right
+  float2( 1.0f, -1.0f), // -- bottom left
+};
+
+[maxvertexcount(4)]
+void GS (point GSPS_INPUT input[1], inout TriangleStream<GSPS_INPUT> TriStream)
+{
+  GSPS_INPUT output;
+
+  for (int i = 0; i < 4; i++) {
+    float2 Pos;
+    Pos = vertices[i] * vGlyphScale + vPosition;
+    Pos = Pos * vInvScreenSize + float2(-1, 1);
+    output.Pos = float4(Pos.xy, 0, 1);
+
+    output.Tex = vertices[i] * float2(1, -1);
+    output.Tex = (output.Tex + vCharCoord) * vTexScale;
+
+    TriStream.Append(output);
+  }
+  TriStream.RestartStrip();
+}
+
+float4 PS(GSPS_INPUT input) : SV_Target
 {
   float4 texColor = txDiffuse.Sample(samPoint, input.Tex);
 
@@ -50,7 +72,7 @@ technique10 Font
   pass P0
   {
     SetVertexShader(CompileShader(vs_4_0, VS()));
-    SetGeometryShader(NULL);
+    SetGeometryShader(CompileShader(gs_4_0, GS()));
     SetPixelShader(CompileShader(ps_4_0, PS()));
   }
 }
diff --git a/src/main.cpp b/src/main.cpp
index 90be717..c79b988 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -923,14 +923,14 @@ void RenderFont()
   UINT offset[] = { 0 };
   g_pd3dDevice->IASetInputLayout(g_pVertexLayoutFont);
   g_pd3dDevice->IASetVertexBuffers(0, g_dwVertexBufferCountFont, g_pVertexBuffersFont, stride, offset);
-  g_pd3dDevice->IASetPrimitiveTopology(D3D10_PRIMITIVE_TOPOLOGY_TRIANGLESTRIP);
+  g_pd3dDevice->IASetPrimitiveTopology(D3D10_PRIMITIVE_TOPOLOGY_POINTLIST);
 
   D3D10_TECHNIQUE_DESC techDesc;
   g_pTechniqueFont->GetDesc(&techDesc);
 
   for (UINT p = 0; p < techDesc.Passes; p++) {
     g_pTechniqueFont->GetPassByIndex(p)->Apply(0);
-    g_pd3dDevice->Draw(4, 0);
+    g_pd3dDevice->Draw(1, 0);
   }
 }