shithub: cstory

--- a/src/Backends/Rendering/OpenGL3.cpp

+++ b/src/Backends/Rendering/OpenGL3.cpp

@@ -25,6 +25,7 @@

 	GLuint texture_id;

 	unsigned int width;

 	unsigned int height;

+	BOOL subpixel_mode;

 } Backend_Glyph;

 typedef struct Coordinate2D

@@ -45,10 +46,13 @@

 static GLuint program_texture;

 static GLuint program_texture_colour_key;

 static GLuint program_colour_fill;

-static GLuint program_glyph;

+static GLuint program_glyph_normal;

+static GLuint program_glyph_subpixel_part1;

+static GLuint program_glyph_subpixel_part2;

 static GLint program_colour_fill_uniform_colour;

-static GLint program_glyph_uniform_colour;

+static GLint program_glyph_normal_uniform_colour;

+static GLint program_glyph_subpixel_part2_uniform_colour;

 static GLuint vertex_array_id;

 static GLuint vertex_buffer_id;

@@ -116,7 +120,7 @@

} \

";

-static const GLchar *fragment_shader_glyph = " \

+static const GLchar *fragment_shader_glyph_normal = " \

 #version 150 core\n \

 uniform sampler2D tex; \

 uniform vec4 colour; \

@@ -128,6 +132,29 @@

} \

";

+static const GLchar *fragment_shader_glyph_subpixel_part1 = " \

+#version 150 core\n \

+uniform sampler2D tex; \

+in vec2 texture_coordinates; \

+out vec4 fragment; \

+void main() \

+{ \

+	fragment = texture2D(tex, texture_coordinates); \

+} \

+";

+static const GLchar *fragment_shader_glyph_subpixel_part2 = " \

+#version 150 core\n \

+uniform sampler2D tex; \

+uniform vec4 colour; \

+in vec2 texture_coordinates; \

+out vec4 fragment; \

+void main() \

+{ \

+	fragment = colour * texture2D(tex, texture_coordinates); \

+} \

+";

 static void GLAPIENTRY MessageCallback(GLenum source, GLenum type, GLuint id, GLenum severity, GLsizei length, const GLchar *message, const void* userParam)

 	(void)source;

@@ -207,8 +234,6 @@

 	glEnable(GL_DEBUG_OUTPUT);

 	glDebugMessageCallback(MessageCallback, 0);

-	glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);

 	glClearColor(0.0f, 0.0f, 0.0f, 1.0f);

 	glClear(GL_COLOR_BUFFER_BIT);

@@ -230,14 +255,17 @@

 	program_texture = CompileShader(vertex_shader_texture, fragment_shader_texture);

 	program_texture_colour_key = CompileShader(vertex_shader_texture, fragment_shader_texture_colour_key);

 	program_colour_fill = CompileShader(vertex_shader_plain, fragment_shader_colour_fill);

-	program_glyph = CompileShader(vertex_shader_texture, fragment_shader_glyph);

+	program_glyph_normal = CompileShader(vertex_shader_texture, fragment_shader_glyph_normal);

+	program_glyph_subpixel_part1 = CompileShader(vertex_shader_texture, fragment_shader_glyph_subpixel_part1);

+	program_glyph_subpixel_part2 = CompileShader(vertex_shader_texture, fragment_shader_glyph_subpixel_part2);

-	if (program_texture == 0 || program_texture_colour_key == 0 || program_colour_fill == 0 || program_glyph == 0)

+	if (program_texture == 0 || program_texture_colour_key == 0 || program_colour_fill == 0 || program_glyph_normal == 0 || program_glyph_subpixel_part1 == 0 || program_glyph_subpixel_part2 == 0)

 		printf("Failed to compile shaders\n");

 	// Get shader uniforms

 	program_colour_fill_uniform_colour = glGetUniformLocation(program_colour_fill, "colour");

-	program_glyph_uniform_colour = glGetUniformLocation(program_glyph, "colour");

+	program_glyph_normal_uniform_colour = glGetUniformLocation(program_glyph_normal, "colour");

+	program_glyph_subpixel_part2_uniform_colour = glGetUniformLocation(program_glyph_subpixel_part2, "colour");

 	// Set up framebuffer (used for surface-to-surface blitting)

 	glGenFramebuffers(1, &framebuffer_id);

@@ -263,7 +291,9 @@

 	glDeleteTextures(1, &framebuffer_surface.texture_id);

 	glDeleteFramebuffers(1, &framebuffer_id);

-	glDeleteProgram(program_glyph);

+	glDeleteProgram(program_glyph_subpixel_part2);

+	glDeleteProgram(program_glyph_subpixel_part1);

+	glDeleteProgram(program_glyph_normal);

 	glDeleteProgram(program_colour_fill);

 	glDeleteProgram(program_texture_colour_key);

 	glDeleteProgram(program_texture);

@@ -491,7 +521,7 @@

 BOOL Backend_SupportsSubpixelGlyph(void)

-	return FALSE;	// Per-component alpha is available as an extension, but I haven't looked into it yet

+	return TRUE;

 Backend_Glyph* Backend_LoadGlyph(const unsigned char *pixels, unsigned int width, unsigned int height, int pitch, unsigned short total_greys, unsigned char pixel_mode)

@@ -501,8 +531,10 @@

 	if (glyph == NULL)

 		return NULL;

-	const int destination_pitch = (width + 3) & ~3;	// Round up to the nearest 4 (OpenGL needs this)

+	const BOOL subpixel_mode = pixel_mode == FONT_PIXEL_MODE_LCD;

+	const int destination_pitch = ((subpixel_mode ? width * 3 : width) + 3) & ~3;	// Round up to the nearest 4 (OpenGL needs this)

 	unsigned char *buffer = (unsigned char*)malloc(destination_pitch * height);

 	if (buffer == NULL)

@@ -513,8 +545,23 @@

 	switch (pixel_mode)

-		// FONT_PIXEL_MODE_LCD is unsupported

+		case FONT_PIXEL_MODE_LCD:

+			for (unsigned int y = 0; y < height; ++y)

+			{

+				const unsigned char *source_pointer = pixels + y * pitch;

+				unsigned char *destination_pointer = buffer + y * destination_pitch;

+				for (unsigned int x = 0; x < width; ++x)

+				{

+					for (unsigned int i = 0; i < 3; ++i)

+					{

+						*destination_pointer++ = (unsigned char)(pow((*source_pointer++ / 255.0), 1.0 / 1.8) * 255.0);

+					}

+				}

+			}

+			break;

 		case FONT_PIXEL_MODE_GRAY:

 			for (unsigned int y = 0; y < height; ++y)

@@ -546,7 +593,7 @@

 	glGenTextures(1, &glyph->texture_id);

 	glBindTexture(GL_TEXTURE_2D, glyph->texture_id);

-	glTexImage2D(GL_TEXTURE_2D, 0, GL_R8, width, height, 0,  GL_RED, GL_UNSIGNED_BYTE, buffer);

+	glTexImage2D(GL_TEXTURE_2D, 0, subpixel_mode ? GL_RGB8 : GL_R8, width, height, 0, subpixel_mode ? GL_RGB : GL_RED, GL_UNSIGNED_BYTE, buffer);

 	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);

 	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);

 	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);

@@ -555,6 +602,7 @@

 	glyph->width = width;

 	glyph->height = height;

+	glyph->subpixel_mode = subpixel_mode;

 	free(buffer);

@@ -579,8 +627,6 @@

 	glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, surface->texture_id, 0);

 	glViewport(0, 0, surface->width, surface->height);

-	glUseProgram(program_glyph);

 	glEnable(GL_BLEND);

 	// Enable texture coordinates, since this uses textures

@@ -593,8 +639,6 @@

 	const GLfloat vertex_top = (y * (2.0f / surface->height)) - 1.0f;

 	const GLfloat vertex_bottom = ((y + glyph->height) * (2.0f / surface->height)) - 1.0f;

-	glUniform4f(program_glyph_uniform_colour, colours[0] / 255.0f, colours[1] / 255.0f, colours[2] / 255.0f, 1.0f);

 	vertex_buffer.texture_coordinates[0].x = 0.0f;

 	vertex_buffer.texture_coordinates[0].y = 0.0f;

 	vertex_buffer.texture_coordinates[1].x = 1.0f;

@@ -614,7 +658,31 @@

 	vertex_buffer.vertexes[3].y = vertex_bottom;

 	glBufferSubData(GL_ARRAY_BUFFER, 0, sizeof(vertex_buffer), &vertex_buffer);

-	glDrawArrays(GL_TRIANGLE_FAN, 0, 4);

+	if (glyph->subpixel_mode)

+	{

+		// Here we're going to draw with per-component alpha.

+		// Since OpenGL doesn't really support this, we have to do it manually:

+		// Step one: attenuate the destination pixels by the alpha

+		glBlendFunc(GL_ZERO, GL_ONE_MINUS_SRC_COLOR);

+		glUseProgram(program_glyph_subpixel_part1);

+		glDrawArrays(GL_TRIANGLE_FAN, 0, 4);

+		// Step two: add the new pixels on top of them

+		glBlendFunc(GL_ONE, GL_ONE);

+		glUseProgram(program_glyph_subpixel_part2);

+		glUniform4f(program_glyph_subpixel_part2_uniform_colour, colours[0] / 255.0f, colours[1] / 255.0f, colours[2] / 255.0f, 1.0f);

+		glDrawArrays(GL_TRIANGLE_FAN, 0, 4);

+	}

+	else

+	{

+		// Here, we just use a regular alpha channel

+		glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);

+		glUseProgram(program_glyph_normal);

+		glUniform4f(program_glyph_normal_uniform_colour, colours[0] / 255.0f, colours[1] / 255.0f, colours[2] / 255.0f, 1.0f);

+		glDrawArrays(GL_TRIANGLE_FAN, 0, 4);

+	}

 void Backend_DrawGlyph(Backend_Surface *surface, Backend_Glyph *glyph, long x, long y, const unsigned char *colours)