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Made the OpenGL 2.1 backend use custom shaders

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Edging towards OpenGL 3.
This commit is contained in:
Clownacy 2019-07-31 03:00:56 +00:00
parent f0809fb901
commit 92476bd30a
1 changed files with 42 additions and 8 deletions
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50
src/Backends/Rendering/OpenGL2.cpp
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@ -27,6 +27,7 @@ typedef struct Backend_Glyph
static SDL_Window *window;
static SDL_GLContext context;
static GLuint normal_program_id;
static GLuint colour_key_program_id;
static GLuint framebuffer_id;
static GLfloat vertex_buffer[4][2];
@ -35,7 +36,26 @@ static GLubyte colour_buffer[4][3];
static Backend_Surface framebuffer_surface;
static const GLchar *fragment_shader_source = " \
static const GLchar *vertex_shader_source = " \
#version 120\n \
void main() \
{ \
gl_FrontColor = gl_Color; \
gl_TexCoord[0] = gl_MultiTexCoord0; \
gl_Position = gl_ModelViewMatrix * gl_Vertex; \
} \
";
static const GLchar *fragment_shader_source_normal = " \
#version 120\n \
uniform sampler2D tex; \
void main() \
{ \
gl_FragColor = gl_Color * texture2D(tex, gl_TexCoord[0].st); \
} \
";
static const GLchar *fragment_shader_source_colour_key = " \
#version 120\n \
uniform sampler2D tex; \
void main() \
@ -49,12 +69,22 @@ void main() \
} \
";
static GLuint CompileShader(const char *fragment_shader_source)
static GLuint CompileShader(const char *vertex_shader_source, const char *fragment_shader_source)
{
GLint shader_status;
GLuint program_id = glCreateProgram();
GLuint vertex_shader = glCreateShader(GL_VERTEX_SHADER);
glShaderSource(vertex_shader, 1, &vertex_shader_source, NULL);
glCompileShader(vertex_shader);
glGetShaderiv(vertex_shader, GL_COMPILE_STATUS, &shader_status);
if (shader_status != GL_TRUE)
return 0;
glAttachShader(program_id, vertex_shader);
GLuint fragment_shader = glCreateShader(GL_FRAGMENT_SHADER);
glShaderSource(fragment_shader, 1, &fragment_shader_source, NULL);
glCompileShader(fragment_shader);
@ -134,8 +164,12 @@ BOOL Backend_Init(SDL_Window *p_window)
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
// Set up our colour-key-enabled fragment shader
colour_key_program_id = CompileShader(fragment_shader_source);
// Set up our shaders
normal_program_id = CompileShader(vertex_shader_source, fragment_shader_source_normal);
colour_key_program_id = CompileShader(vertex_shader_source, fragment_shader_source_colour_key);
if (normal_program_id == 0 || colour_key_program_id == 0)
printf("Failed to compile shaders\n");
// Set up framebuffer (used for surface-to-surface blitting)
glGenFramebuffersEXT(1, &framebuffer_id);
@ -165,7 +199,7 @@ void Backend_Deinit(void)
void Backend_DrawScreen(void)
{
// Disable colour-keying
glUseProgram(0);
glUseProgram(normal_program_id);
// Target actual screen, and not our framebuffer
glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);
@ -271,7 +305,7 @@ static void BlitCommon(Backend_Surface *source_surface, const RECT *rect, long x
return;
// Switch to colour-key shader if we have to
glUseProgram(colour_key ? colour_key_program_id : 0);
glUseProgram(colour_key ? colour_key_program_id : normal_program_id);
glBindTexture(GL_TEXTURE_2D, source_surface->texture_id);
@ -338,7 +372,7 @@ static void ColourFillCommon(const RECT *rect, unsigned char red, unsigned char
return;
// Disable colour-keying
glUseProgram(0);
glUseProgram(normal_program_id);
// Use blank default texture, for a solid colour-fill
glBindTexture(GL_TEXTURE_2D, 0);
@ -472,7 +506,7 @@ void Backend_UnloadGlyph(Backend_Glyph *glyph)
static void DrawGlyphCommon(Backend_Glyph *glyph, long x, long y, const unsigned char *colours)
{
// Disable colour-keying
glUseProgram(0);
glUseProgram(normal_program_id);
glBindTexture(GL_TEXTURE_2D, glyph->texture_id);