Fix 2d stippling of hovered and selected faces.

This was broken in ec07516.

res/CMakeLists.txt

@@ -211,7 +211,6 @@ add_resources(
     shaders/imesh_point.vert
     shaders/imesh_tex.frag
     shaders/imesh_texa.frag
-    shaders/imesh_texr.frag
     shaders/imesh_tex.vert
     shaders/mesh.frag
     shaders/mesh.vert

res/shaders/imesh_texa.frag

@@ -9,5 +9,5 @@ uniform sampler2D texture;
 varying vec2 fragTex;
 
 void main() {
-    gl_FragColor = vec4(color.rgb, color.a * texture2D(texture, fragTex).a);
+    gl_FragColor = vec4(color.rgb, color.a * texture2D(texture, fragTex).TEX_ALPHA);
 }

res/shaders/imesh_texr.frag

@@ -1,13 +0,0 @@
-//-----------------------------------------------------------------------------
-// Indexed Mesh rendering shader
-//
-// Copyright 2016 Aleksey Egorov
-//-----------------------------------------------------------------------------
-uniform vec4 color;
-uniform sampler2D texture;
-
-varying vec2 fragTex;
-
-void main() {
-    gl_FragColor = vec4(color.rgb, color.a * texture2D(texture, fragTex).r);
-}

res/shaders/mesh_fill.frag

@@ -7,6 +7,6 @@ uniform vec4 color;
 uniform sampler2D texture;
 
 void main() {
-    if(texture2D(texture, gl_FragCoord.xy / 32.0).a < 0.5) discard;
+    if(texture2D(texture, gl_FragCoord.xy / 32.0).TEX_ALPHA < 0.5) discard;
     gl_FragColor = color;
 }

src/render/gl2shader.cpp

@@ -84,12 +84,21 @@ static GLuint CompileShader(const std::string &res, GLenum type) {
     // the `precision` keyword entirely, because that's clearly how minor versions work.
     // Christ, what a trash fire.
 
-    std::string src(resData, size);
+    const char *prelude;
 #if defined(HAVE_GLES)
-    src = "#version 100\nprecision highp float;\n" + src;
+    prelude = R"(
+#version 100
+#define TEX_ALPHA a
+precision highp float;
+)";
 #else
-    src = "#version 120\n" + src;
+    prelude = R"(
+#version 120
+#define TEX_ALPHA r
+)";
 #endif
+    std::string src(resData, size);
+    src = prelude + src;
 
     GLuint shader = glCreateShader(type);
     ssassert(shader != 0, "glCreateShader failed");