123 lines
3.4 KiB
C
123 lines
3.4 KiB
C
#include "twn_gl_any_rendering_c.h"
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#include "twn_draw_c.h"
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#include "twn_engine_context_c.h"
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#include <stb_ds.h>
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#ifdef EMSCRIPTEN
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#include <GLES2/gl2.h>
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#else
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#include <glad/glad.h>
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#endif
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void setup_viewport(int x, int y, int width, int height) {
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glViewport(x, y, width, height);
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}
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VertexBuffer create_vertex_buffer(void) {
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GLuint result;
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glGenBuffers(1, &result);
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return result;
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}
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void delete_vertex_buffer(VertexBuffer buffer) {
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glDeleteBuffers(1, &buffer);
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}
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void specify_vertex_buffer(VertexBuffer buffer, void const *data, size_t bytes) {
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glBindBuffer(GL_ARRAY_BUFFER, buffer);
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glBufferData(GL_ARRAY_BUFFER, bytes, data, GL_STREAM_DRAW);
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}
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VertexBuffer get_quad_element_buffer(void) {
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static VertexBuffer buffer = 0;
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/* it's only generated once at runtime */
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/* TODO: use builder interface, not direct calls (glMapBuffer isn't portable) */
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if (buffer == 0) {
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buffer = create_vertex_buffer();
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VertexBufferBuilder builder = build_vertex_buffer(buffer, sizeof (GLshort) * QUAD_ELEMENT_BUFFER_LENGTH * 6 );
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for (size_t i = 0; i < QUAD_ELEMENT_BUFFER_LENGTH; ++i) {
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GLshort indices[6];
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indices[0] = (GLshort)(i * 4 + 0);
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indices[1] = (GLshort)(i * 4 + 1);
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indices[2] = (GLshort)(i * 4 + 2);
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indices[3] = (GLshort)(i * 4 + 2);
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indices[4] = (GLshort)(i * 4 + 3);
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indices[5] = (GLshort)(i * 4 + 0);
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push_to_vertex_buffer_builder(&builder, indices, sizeof indices);
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}
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}
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SDL_assert_always(buffer);
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return buffer;
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}
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VertexBuffer get_circle_element_buffer(void) {
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static VertexBuffer buffer = 0;
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if (buffer == 0) {
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buffer = create_vertex_buffer();
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VertexBufferBuilder builder = build_vertex_buffer(buffer, sizeof (GLshort) * (CIRCLE_VERTICES_MAX - 2) * 3);
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for (size_t i = 1; i < CIRCLE_VERTICES_MAX - 1; ++i) {
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/* first one is center point index, always zero */
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GLshort indices[3];
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indices[0] = 0;
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/* generated point index */
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indices[1] = (GLshort)i;
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indices[2] = (GLshort)i + 1;
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push_to_vertex_buffer_builder(&builder, indices, sizeof indices);
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}
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}
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SDL_assert_always(buffer);
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return buffer;
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}
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/* potentially double buffered array of vertex array handles */
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/* we assume they will be refilled fully each frame */
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static size_t scratch_va_front_used, scratch_va_back_used;
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static GLuint *front_scratch_vertex_arrays, *back_scratch_vertex_arrays;
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static GLuint **current_scratch_vertex_array = &front_scratch_vertex_arrays;
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void restart_scratch_vertex_arrays(void) {
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scratch_va_front_used = 0;
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scratch_va_back_used = 0;
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if (ctx.render_double_buffered) {
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current_scratch_vertex_array = current_scratch_vertex_array == &front_scratch_vertex_arrays ?
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&back_scratch_vertex_arrays : &front_scratch_vertex_arrays;
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}
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}
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GLuint get_scratch_vertex_array(void) {
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size_t *used = current_scratch_vertex_array == &front_scratch_vertex_arrays ?
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&scratch_va_front_used : &scratch_va_back_used;
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if (arrlenu(*current_scratch_vertex_array) <= *used) {
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GLuint handle;
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glGenBuffers(1, &handle);
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arrpush(*current_scratch_vertex_array, handle);
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}
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(*used)++;
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return (*current_scratch_vertex_array)[*used - 1];
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}
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