From 844ad3b073d48cfeccce32a35d2e02ea0b29552f Mon Sep 17 00:00:00 2001
From: Konstantin Nazarov <mail@knazarov.com>
Date: Sun, 22 Dec 2024 02:18:02 +0000
Subject: [PATCH] Implement paletted framebuffer (320x200 for now)

---
 example/example.c   |  9 +++++----
 src/framebuffer.cpp | 32 ++++++++++++++++++++++++--------
 src/vm.hpp          |  4 ++++
 3 files changed, 33 insertions(+), 12 deletions(-)

diff --git a/example/example.c b/example/example.c
index 6a9f074..7a15378 100644
--- a/example/example.c
+++ b/example/example.c
@@ -2,6 +2,7 @@
 
 typedef unsigned long long uint64_t;
 typedef unsigned long uint32_t;
+typedef unsigned char uint8_t;
 #define MTIME_BASE 0x0200BFF8
 
 volatile uint32_t* mtime_upper = (uint32_t*)(MTIME_BASE+4);
@@ -36,10 +37,10 @@ int fib(int n) {
 
 void draw() {
   for (int k = 0; k < 200; k++) {
-    for (int i = 0; i< 640; i++) {
-      for (int j = 0; j < 480; j++) {
-        uint32_t color = i*(j + k);
-        uint32_t* addr = (uint32_t*)(FRAMEBUFFER_BASE + ((j*640) + i) *4);
+    for (int i = 0; i< 320; i++) {
+      for (int j = 0; j < 200; j++) {
+        uint8_t color = i*(j + k);
+        uint8_t* addr = (uint8_t*)(FRAMEBUFFER_BASE + (j*320) + i);
         *addr = color;
       }
     }
diff --git a/src/framebuffer.cpp b/src/framebuffer.cpp
index 9ffc275..4c20425 100644
--- a/src/framebuffer.cpp
+++ b/src/framebuffer.cpp
@@ -9,12 +9,21 @@ SDL_Window* window = nullptr;
 SDL_Renderer* renderer = nullptr;
 SDL_Texture* texture = nullptr;
 
-Framebuffer::Framebuffer() : Device(FRAMEBUFFER_ADDR, 640 * 480 * 4) {
+#define FB_WIDTH 320
+#define FB_HEIGHT 200
+#define FB_SCALE 2
+#define FB_OFFSET 0x10000
+
+Framebuffer::Framebuffer()
+    : Device(FRAMEBUFFER_ADDR, FB_WIDTH * FB_HEIGHT + FB_OFFSET),
+      width(FB_WIDTH),
+      height(FB_HEIGHT),
+      buf(FB_WIDTH * FB_HEIGHT, 0) {
   if (SDL_Init(SDL_INIT_VIDEO) < 0) {
     throw std::runtime_error("Failed to initialize SDL");
   }
   window = SDL_CreateWindow("rve Framebuffer", SDL_WINDOWPOS_CENTERED,
-                            SDL_WINDOWPOS_CENTERED, 640, 480, 0);
+                            SDL_WINDOWPOS_CENTERED, width, height, 0);
   if (!window) {
     throw std::runtime_error("Failed to create SDL window");
   }
@@ -33,7 +42,7 @@ Framebuffer::Framebuffer() : Device(FRAMEBUFFER_ADDR, 640 * 480 * 4) {
     throw std::runtime_error("Failed to create SDL renderer");
   }
   texture = SDL_CreateTexture(renderer, SDL_PIXELFORMAT_ARGB8888,
-                              SDL_TEXTUREACCESS_STREAMING, 640, 480);
+                              SDL_TEXTUREACCESS_STREAMING, width, height);
   if (!texture) {
     throw std::runtime_error("Failed to create SDL texture");
   }
@@ -44,8 +53,15 @@ Framebuffer::Framebuffer() : Device(FRAMEBUFFER_ADDR, 640 * 480 * 4) {
 }
 
 void Framebuffer::draw() {
-  SDL_UpdateTexture(texture, nullptr, &mem[0],
-                    640 * 4);  // Update the SDL texture
+  for (size_t i = 0; i < width * height; i++) {
+    uint8_t color = mem[i + FB_OFFSET];
+    uint32_t cmap = ((uint32_t*)&mem[0])[color];
+
+    buf[i] = cmap;
+  }
+
+  SDL_UpdateTexture(texture, nullptr, &buf[0],
+                    width * 4);  // Update the SDL texture
   SDL_RenderClear(renderer);
   SDL_RenderCopy(renderer, texture, nullptr, nullptr);
   SDL_RenderPresent(renderer);
@@ -54,7 +70,7 @@ void Framebuffer::draw() {
 void Framebuffer::write_mem_u8(uint8_t* src, size_t addr) {
   Device::write_mem_u8(src, addr);
 
-  if (addr + 1 == base() + (640 * 480) * 4) {
+  if (addr + 1 == base() + width * height + FB_OFFSET) {
     // draw to the screen when the last byte is written
     draw();
   }
@@ -63,7 +79,7 @@ void Framebuffer::write_mem_u8(uint8_t* src, size_t addr) {
 void Framebuffer::write_mem_u16(uint16_t* src, size_t addr) {
   Device::write_mem_u16(src, addr);
 
-  if (addr + 2 == base() + (640 * 480) * 4) {
+  if (addr + 2 == base() + width * height + FB_OFFSET) {
     // draw to the screen when the last byte is written
     draw();
   }
@@ -72,7 +88,7 @@ void Framebuffer::write_mem_u16(uint16_t* src, size_t addr) {
 void Framebuffer::write_mem_u32(uint32_t* src, size_t addr) {
   Device::write_mem_u32(src, addr);
 
-  if (addr + 4 == base() + (640 * 480) * 4) {
+  if (addr + 4 == base() + width * height + FB_OFFSET) {
     // draw to the screen when the last byte is written
     draw();
   }
diff --git a/src/vm.hpp b/src/vm.hpp
index 478f8a7..a9c3458 100644
--- a/src/vm.hpp
+++ b/src/vm.hpp
@@ -114,6 +114,10 @@ class Framebuffer final : public Device {
 
  protected:
   void draw();
+
+  size_t width;
+  size_t height;
+  std::vector<uint32_t> buf;
 };
 
 class VM {