support both GLES 3.0 and GL 3.2

Author: tophyr

renderer/CMakeLists.txt

@@ -3,6 +3,8 @@ cmake_path(SET SHADERS_H NORMALIZE ${GENERATED_HEADERS}/shaders.h)
 set(SHADERS
   shaders/fragment.glsl
   shaders/vertex.glsl
+  shaders/version_300_es.glsl
+  shaders/version_150_core.glsl
 )
 add_custom_command(
   OUTPUT ${SHADERS_H}

renderer/HardwareOpenGL.cpp

@@ -68,12 +68,15 @@ renderer_type Renderer_type = RENDERER_OPENGL;
 int WindowGL = 0;
 
 struct Renderer {
-  Renderer() : shader_{shaders::vertex, shaders::fragment, {
+  Renderer() : shader_{
+    std::string{kGlslVersion} + std::string{shaders::vertex},
+    std::string{kGlslVersion} + std::string{shaders::fragment},
+    {
       vertexAttrib(3, GL_FLOAT, GL_FALSE, &PosColorUV2Vertex::pos, "in_pos"),
       vertexAttrib(4, GL_FLOAT, GL_FALSE, &PosColorUV2Vertex::color, "in_color"),
       vertexAttrib(2, GL_FLOAT, GL_FALSE, &PosColorUV2Vertex::uv0, "in_uv0"),
       vertexAttrib(2, GL_FLOAT, GL_FALSE, &PosColorUV2Vertex::uv1, "in_uv1")
-  }} {
+    }} {
     shader_.Use();
 
     // these are effectively just constants, for now
@@ -143,6 +146,13 @@ struct Renderer {
   glm::mat4x4 projection_;
   GLint texture_enable_{};
   ShaderProgram<PosColorUV2Vertex> shader_;
+
+  static constexpr auto kGlslVersion =
+#if defined(ANDROID)
+      shaders::version_300_es;
+#else
+  shaders::version_150_core;
+#endif
 };
 std::optional<Renderer> gRenderer;
 
@@ -424,8 +434,10 @@ int opengl_Setup(oeApplication *app, int *width, int *height) {
   SDL_GL_SetAttribute(SDL_GL_DEPTH_SIZE, 16);
   SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
   SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 3);
+#if !defined(ANDROID)
   SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 2);
   SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_CORE);
+#endif
   Uint32 flags = SDL_WINDOW_OPENGL;
 
   if (fullscreen) {

renderer/shaders/fragment.glsl

@@ -1,4 +1,4 @@
-#version 150 core
+// version must be prepended to this file
 
 /*
 * Descent 3
@@ -18,6 +18,8 @@
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
 
+precision highp float;
+
 in vec4 vertex_color;
 in vec2 vertex_uv0;
 in vec2 vertex_uv1;
@@ -50,9 +52,9 @@ void main()
         * max(texture(u_texture0, vertex_uv0), vec4(float(!bool((u_texture_enable >> 0) & 1))))
         * max(texture(u_texture1, vertex_uv1), vec4(float(!bool((u_texture_enable >> 1) & 1))));
 
-    float fog_factor = clamp((u_fog_end - length(vertex_modelview_pos)) * branchless_invert_or_zero(u_fog_end - u_fog_start), 0, 1);
+    float fog_factor = clamp((u_fog_end - length(vertex_modelview_pos)) * branchless_invert_or_zero(u_fog_end - u_fog_start), 0.0, 1.0);
     // out_color is unchanged when fog_factor is 1 (ie, fog distance == u_fog_start). thus, to disable,
     // fog_factor must also be 1. invert u_fog_enable (so that it is 1 when disabled) and take the max.
     fog_factor = max(fog_factor, float(!u_fog_enable));
-    out_color = out_color * fog_factor + (1 - fog_factor) * u_fog_color;
+    out_color = out_color * fog_factor + (1.0 - fog_factor) * u_fog_color;
 }

renderer/shaders/version_150_core.glsl

@@ -0,0 +1 @@
+#version 150 core

renderer/shaders/version_300_es.glsl

@@ -0,0 +1 @@
+#version 300 es

renderer/shaders/vertex.glsl

@@ -1,4 +1,4 @@
-#version 150 core
+// version must be prepended to this file
 
 /*
 * Descent 3