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#include <renderer/RSoftwareBackend.hpp>
#include <SDL3/SDL_video.h>
#include <GL/glew.h>
#include <algorithm>
#include <cstdlib>
#include <cstdio>
RSoftwareBackend::RSoftwareBackend(SDL_Window* window, Renderer& renderer)
: m_window {window}
, m_renderer {renderer}
{
m_canvas.rshift = 0;
m_canvas.gshift = 8;
m_canvas.bshift = 16;
m_canvas.ashift = 24;
m_canvas.pixels = nullptr;
glEnable(GL_TEXTURE_2D);
glActiveTexture(GL_TEXTURE0);
glGenTextures(1, &m_gltexture_id);
glBindTexture(GL_TEXTURE_2D, m_gltexture_id);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
}
void
RSoftwareBackend::ResizeCanvas(int32_t w, int32_t h)
{
size_t realloc_size = (size_t)(w * h) * sizeof(m_canvas.pixels[0]);
void *realloc_data = realloc(m_canvas.pixels, realloc_size);
if (!realloc_data) {
printf("could not resize offscreen buffer\n");
return;
}
m_canvas.w = w;
m_canvas.h = h;
m_canvas.pixels = (uint32_t*)realloc_data;
}
void
RSoftwareBackend::Draw()
{
ResizeCanvas(m_renderer.m_screen_w, m_renderer.m_screen_h);
SortRenderEntities();
REntity_Rectangle clear_rect = {
REntityType_Rectangle,
0, 0,
(float)(m_canvas.w-1), (float)(m_canvas.h-1),
0.0f,
m_renderer.m_clear_color
};
DrawRectangle(clear_rect);
float z = -1;
for (RSortEntry sort_entry : m_renderer.m_sort_entries) {
if (sort_entry.z >= z) {
z = sort_entry.z;
}
REntity& entity = m_renderer.m_render_entities[sort_entry.entity_index];
switch (entity.type) {
case REntityType_Rectangle: {
DrawRectangle(entity.rect);
} break;
case REntityType_MonoBitmap: {
Color color = {0.0f, 0.0f, 0.0f, 1.0f};
DrawMonoBitmap(entity.bitmap, color);
} break;
default:;
}
}
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, m_gltexture_id);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, m_canvas.w, m_canvas.h, 0, GL_RGBA, GL_UNSIGNED_BYTE, m_canvas.pixels);
glBegin(GL_QUADS);
glTexCoord2f(0.0f, 0.0f); glVertex2f(-1.0f, -1.0f);
glTexCoord2f(1.0f, 0.0f); glVertex2f( 1.0f, -1.0f);
glTexCoord2f(1.0f, 1.0f); glVertex2f( 1.0f, 1.0f);
glTexCoord2f(0.0f, 1.0f); glVertex2f(-1.0f, 1.0f);
glEnd();
glBindTexture(GL_TEXTURE_2D, 0);
}
void
RSoftwareBackend::SortRenderEntities()
{
auto& sort_entries = m_renderer.m_sort_entries;
std::sort(sort_entries.begin(), sort_entries.end(),
[](const RSortEntry& e1, const RSortEntry& e2) {
return e1.z < e2.z;
});
}
void
RSoftwareBackend::DrawRectangle(REntity_Rectangle& rect)
{
int32_t xmin = m_renderer.WorldXToScreenX(rect.x0);
int32_t ymin = m_renderer.WorldYToScreenY(rect.y0);
int32_t xmax = m_renderer.WorldXToScreenX(rect.x1);
int32_t ymax = m_renderer.WorldYToScreenY(rect.y1);
if (xmin < 0) {
xmin = 0;
}
if (ymin < 0) {
ymin = 0;
}
if (xmax >= m_canvas.w) {
xmax = m_canvas.w - 1;
}
if (ymax >= m_canvas.h) {
ymax = m_canvas.h - 1;
}
uint32_t rshift = m_canvas.rshift;
uint32_t gshift = m_canvas.gshift;
uint32_t bshift = m_canvas.bshift;
for (int32_t y = ymin; y <= ymax; ++y) {
uint32_t *pixel = m_canvas.pixels + y * m_canvas.w + xmin;
for (int32_t x = xmin; x <= xmax; ++x) {
uint32_t r = (uint32_t)(rect.color.r * 255.0f);
uint32_t g = (uint32_t)(rect.color.g * 255.0f);
uint32_t b = (uint32_t)(rect.color.b * 255.0f);
uint32_t val = r << rshift | g << gshift | b << bshift;
*pixel++ = val;
}
}
}
void
RSoftwareBackend::DrawMonoBitmap(REntity_MonoBitmap& mono_bitmap, Color color)
{
int32_t x0 = (int32_t)mono_bitmap.x;
int32_t y0 = (int32_t)mono_bitmap.y;
int32_t x1 = (int32_t)mono_bitmap.x + mono_bitmap.w - 1;
int32_t y1 = (int32_t)mono_bitmap.y + mono_bitmap.h - 1;
int32_t cut_left = 0;
int32_t cut_bot = 0;
if (x0 < 0) {
cut_left = x0;
x0 = 0;
}
if (y0 < 0) {
cut_bot = y0;
y0 = 0;
}
if (x1 >= m_canvas.w) {
x1 = m_canvas.w - 1;
}
if (y1 >= m_canvas.h) {
y1 = m_canvas.h - 1;
}
uint32_t rshift = m_canvas.rshift;
uint32_t gshift = m_canvas.gshift;
uint32_t bshift = m_canvas.bshift;
uint8_t* grayscale = (uint8_t*)mono_bitmap.data + (-cut_bot * mono_bitmap.w) + (-cut_left);
uint32_t* rgba = m_canvas.pixels + y0 * m_canvas.w + x0;
for (int32_t y = y0; y <= y1; y++) {
uint8_t *grayscale_pixels = grayscale;
uint32_t *rgba_pixels = rgba;
for (int32_t x = x0; x <= x1; x++) {
float alpha = *grayscale_pixels / 255.0f;
// Todo: we do not want to blend with existing color!
uint32_t rgba_result = *rgba_pixels;
float r0 = (rgba_result >> rshift) & 0xff;
float g0 = (rgba_result >> gshift) & 0xff;
float b0 = (rgba_result >> bshift) & 0xff;
float r1 = r0 + (color.r - r0)*alpha;
float g1 = g0 + (color.g - g0)*alpha;
float b1 = b0 + (color.b - b0)*alpha;
rgba_result = (uint32_t)r1 << rshift | (uint32_t)g1 << gshift | (uint32_t)b1 << bshift;
*rgba_pixels = rgba_result;
grayscale_pixels++;
rgba_pixels++;
}
grayscale += mono_bitmap.w;
rgba += m_canvas.w;
}
}
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