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#include "imgui.h"
#include <renderer/RSoftwareBackend.hpp>
#include <SDL3/SDL_video.h>
#include <GL/glew.h>
#include <algorithm>
#include <cstdlib>
#include <cstdio>
RSoftwareBackend::RSoftwareBackend(Renderer& renderer)
: 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();
for (RSortEntry sort_entry : m_renderer.m_sort_entries) {
REntity& entity = m_renderer.m_render_entities[sort_entry.entity_index];
switch (entity.type) {
case REntityType_Rectangle: {
DrawRectangle(entity.rect);
} break;
case REntityType_AlphaBitmap: {
DrawAlphaBitmap(entity.bitmap);
} break;
case REntityType_Text: {
DrawText(entity.text);
}; break;
case REntityType_Circle: {
}; 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& entity)
{
int32_t xmin = m_renderer.WorldXToScreenX(entity.rect.x0);
int32_t ymin = m_renderer.WorldYToScreenY(entity.rect.y0);
int32_t xmax = m_renderer.WorldXToScreenX(entity.rect.x1);
int32_t ymax = m_renderer.WorldYToScreenY(entity.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)(entity.color.r * 255.0f);
uint32_t g = (uint32_t)(entity.color.g * 255.0f);
uint32_t b = (uint32_t)(entity.color.b * 255.0f);
uint32_t val = r << rshift | g << gshift | b << bshift;
*pixel++ = val;
}
}
}
void
RSoftwareBackend::DrawAlphaBitmap(REntity_AlphaBitmap& entity)
{
int32_t x0 = m_renderer.WorldXToScreenX(entity.pos.x);
int32_t y0 = m_renderer.WorldYToScreenY(entity.pos.y);
int32_t x1 = x0 + entity.bitmap.w - 1;
int32_t y1 = y0 + entity.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;
}
uint8_t* alpha_row = (uint8_t*)entity.bitmap.pixels.get() + (-cut_bot * entity.bitmap.w) + (-cut_left);
uint32_t* rgba_row = m_canvas.pixels + y0 * m_canvas.w + x0;
for (int32_t y = y0; y <= y1; y++) {
uint8_t* alpha = alpha_row;
uint32_t* rgba = rgba_row;
for (int32_t x = x0; x <= x1; x++) {
if (*alpha == 0) {
alpha++;
rgba++;
continue;
}
float alphaf = *alpha / 255.0f;
float r1 = entity.color.r * alphaf;
float g1 = entity.color.g * alphaf;
float b1 = entity.color.b * alphaf;
uint32_t r2 = uint32_t(r1 * 255.0f) << m_canvas.rshift;
uint32_t g2 = uint32_t(g1 * 255.0f) << m_canvas.gshift;
uint32_t b2 = uint32_t(b1 * 255.0f) << m_canvas.bshift;
uint32_t rgba_result = r2 | g2 | b2;
*rgba = rgba_result;
alpha++;
rgba++;
}
alpha_row += entity.bitmap.w;
rgba_row += m_canvas.w;
}
}
void
RSoftwareBackend::DrawText(REntity_Text& entity)
{
int32_t xscreen = m_renderer.WorldXToScreenX(entity.pos.x);
int32_t yscreen = m_renderer.WorldYToScreenY(entity.pos.y);
for (char32_t ch : entity.text) {
Glyph& glyph = entity.font.GetGlyph(ch);
int32_t x = xscreen + glyph.xoff;
int32_t y = yscreen + glyph.yoff;
DrawTextGlyph(glyph, entity.color, x, y);
xscreen += glyph.xadvance;
}
}
void
RSoftwareBackend::DrawTextGlyph(Glyph& glyph, Color color, int32_t xscreen, int32_t yscreen)
{
int32_t x0 = xscreen;
int32_t y0 = yscreen;
int32_t x1 = x0 + glyph.bitmap.w - 1;
int32_t y1 = y0 + glyph.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;
}
uint8_t* alpha_row = (uint8_t*)glyph.bitmap.pixels.get() + (-cut_bot * glyph.bitmap.w) + (-cut_left);
uint32_t* rgba_row = m_canvas.pixels + y0 * m_canvas.w + x0;
for (int32_t y = y0; y <= y1; y++) {
uint8_t* alpha = alpha_row;
uint32_t* rgba = rgba_row;
for (int32_t x = x0; x <= x1; x++) {
if (*alpha == 0) {
alpha++;
rgba++;
continue;
}
float alphaf = *alpha / 255.0f;
float r1 = color.r * alphaf;
float g1 = color.g * alphaf;
float b1 = color.b * alphaf;
uint32_t r2 = uint32_t(r1 * 255.0f) << m_canvas.rshift;
uint32_t g2 = uint32_t(g1 * 255.0f) << m_canvas.gshift;
uint32_t b2 = uint32_t(b1 * 255.0f) << m_canvas.bshift;
uint32_t rgba_result = r2 | g2 | b2;
*rgba = rgba_result;
alpha++;
rgba++;
}
alpha_row += glyph.bitmap.w;
rgba_row += m_canvas.w;
}
}
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