From 55bcdf37342d782c723166de54ff031d09b1281f Mon Sep 17 00:00:00 2001
From: 3gg <3gg@shellblade.net>
Date: Wed, 15 Oct 2025 19:32:21 -0700
Subject: Clear framebuffer to pink

---
 src/framebuffer.c | 84 +++++++++++++++++++++++++++++++++----------------------
 1 file changed, 50 insertions(+), 34 deletions(-)

(limited to 'src/framebuffer.c')

diff --git a/src/framebuffer.c b/src/framebuffer.c
index c3845b1..6505ace 100644
--- a/src/framebuffer.c
+++ b/src/framebuffer.c
@@ -1,58 +1,74 @@
 #include <framebuffer.h>
 
 #include <mailbox.h>
+#include <string.h>
 
 #include <stddef.h>
 #include <stdint.h>
 
 #define WIDTH     640
 #define HEIGHT    480
-#define DEPTH      32
+#define DEPTH      24
 #define ALIGNMENT  16 // Framebuffer byte alignment.
 
-typedef struct Framebuffer {
-  volatile void* pixels;
-  size_t         size;
-} Framebuffer;
-
 static Framebuffer framebuffer = {};
 
 bool framebuffer_init(uint32_t* error) {
-  MAIL_T uint32_t ConfigureScreen[20] = {
-    80, // Size in bytes, aligned to MAIL_ALIGN.
-    MAILBOX_REQUEST,
-    TAG_FRAMEBUFFER_SET_PHYSICAL_SCREEN_SIZE, 8, MAILBOX_REQUEST, WIDTH, HEIGHT,
-    TAG_FRAMEBUFFER_SET_VIRTUAL_SCREEN_SIZE,  8, MAILBOX_REQUEST, WIDTH, HEIGHT,
-    TAG_FRAMEBUFFER_SET_DEPTH,                4, MAILBOX_REQUEST, DEPTH,
-    TAG_END,
-    0, 0, 0 // Padding.
-  };
-  mbox_write(PROPERTY_CHANNEL, ConfigureScreen);
-  const Mail* response = mbox_read(PROPERTY_CHANNEL);
-  if (response->code != MAILBOX_SUCCESS) {
-    goto end;
-  }
-  
-  MAIL_T uint32_t InitFramebuffer[8] = {
-    32, // Size in bytes, aligned to MAIL_ALIGN.
-    MAILBOX_REQUEST,
-    TAG_FRAMEBUFFER_ALLOCATE, 8, MAILBOX_REQUEST, ALIGNMENT, 0,
-    TAG_END
+  // TODO: We can combine both messages, this one and the one below, into a
+  // single array and make a single call to mbox_write().
+  MAIL_T uint32_t InitFramebuffer[24] = {
+    /*00*/96, // Size in bytes, aligned to MAIL_ALIGN.
+    /*01*/MAILBOX_REQUEST,
+    /*02*/TAG_FRAMEBUFFER_SET_PHYSICAL_SCREEN_SIZE, 8, MAILBOX_REQUEST, WIDTH, HEIGHT,
+    /*07*/TAG_FRAMEBUFFER_SET_VIRTUAL_SCREEN_SIZE,  8, MAILBOX_REQUEST, WIDTH, HEIGHT,
+    /*12*/TAG_FRAMEBUFFER_SET_DEPTH,                4, MAILBOX_REQUEST, DEPTH,
+    /*16*/TAG_FRAMEBUFFER_ALLOCATE,                 8, MAILBOX_REQUEST, ALIGNMENT, 0,
+    /*21*/TAG_END,
+    /*22*/0, 0 // Padding.
   };
-  mbox_write(PROPERTY_CHANNEL, InitFramebuffer);
-  response = mbox_read(PROPERTY_CHANNEL);
-  if (response->code != MAILBOX_SUCCESS) {
+  const uint32_t result = mbox_write(PROPERTY_CHANNEL, InitFramebuffer);
+  if (result != MAILBOX_SUCCESS) {
     goto end;
   }
   
   // The input mail is overwritten with the response.
+  //
+  // TAG_FRAMEBUFFER_ALLOCATE response:
   //   u32 fb base address
   //   u32 fb size
-  framebuffer.pixels = (void*)(uintptr_t)InitFramebuffer[5];
-  framebuffer.size   = InitFramebuffer[6];
-  
+  // TODO: Do we need & 0x3FFFFFFF? Something about converting GPU address space
+  // to ARM address space.
+  // TODO: Should we read back the pitch, or does pitch match width?
+  framebuffer = (Framebuffer) {
+    .pixels = (Pixel*)((uintptr_t)InitFramebuffer[19] & 0x3FFFFFFF),
+    .size   = InitFramebuffer[20],
+    .width  = InitFramebuffer[5],
+    .height = InitFramebuffer[6],
+    .depth  = InitFramebuffer[15]
+  };
+
 end:
-  *error = response->code;
-  return response->code == MAILBOX_SUCCESS;
+  *error = result;
+  return result == MAILBOX_SUCCESS;
+}
+
+const Framebuffer* framebuffer_get() {
+  return &framebuffer;
+}
+
+void framebuffer_present(const Pixel* pixels) {
+  memcpy(framebuffer.pixels, pixels, framebuffer.size);
+}
+
+void framebuffer_clear(Pixel colour) {
+  const uint32_t num_channels = framebuffer.depth / 8;
+  const uint32_t num_pixels   = framebuffer.size  / num_channels;
+  volatile Pixel* fb = framebuffer.pixels;
+  for (size_t i = 0; i < num_pixels; i++) {
+    fb->r = colour.r;
+    fb->g = colour.g;
+    fb->b = colour.b;
+    fb++;
+  }
 }
 
-- 
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