From 12f2060edb5eb26be4243e124a487dfe2caeb9e9 Mon Sep 17 00:00:00 2001
From: Alexandros Mandravillis <Alexbeav@live.com>
Date: Mon, 31 Aug 2026 03:01:23 +0300
Subject: [PATCH] Present full depth24 scanout canvas

---
 runtime/include/display_scanout.h    |  9 +++++++++
 runtime/src/main.cpp                 | 11 ++++++-----
 runtime/tests/test_display_scanout.c |  8 ++++++++
 3 files changed, 23 insertions(+), 5 deletions(-)

diff --git a/runtime/include/display_scanout.h b/runtime/include/display_scanout.h
index 64ab7b1d..b2f24dd5 100644
--- a/runtime/include/display_scanout.h
+++ b/runtime/include/display_scanout.h
@@ -14,6 +14,15 @@ typedef struct {
     int valid;
 } PsxDisplayVerticalLayout;
 
+/* Depth24 staging expands the visible source into the full active-video
+ * canvas. Every presentation backend must therefore consume the canvas
+ * height, while ordinary 15-bit display keeps its source height. */
+static inline uint32_t psx_display_present_height(
+    int depth24, uint32_t source_height, uint32_t canvas_height)
+{
+    return depth24 && canvas_height != 0u ? canvas_height : source_height;
+}
+
 /* Intersect a GP1(07h) range with the PAL or NTSC active region. The canvas
  * preserves the television scanout position without discarding visible VRAM
  * rows. source_skip_y owns rows before the active region; canvas_origin_y owns
diff --git a/runtime/src/main.cpp b/runtime/src/main.cpp
index 90830341..6ca20e8d 100644
--- a/runtime/src/main.cpp
+++ b/runtime/src/main.cpp
@@ -6970,7 +6970,7 @@ static NetplayVblankEpilogue sdl_vblank_present_body(void) {
 
     /* ---- Display from our VRAM ---- */
     probe_reached = 1;
-    uint32_t w = 0, h = 0;
+    uint32_t w = 0, h = 0, present_h = 0;
     uint32_t present_w = 0;  /* display width actually presented (w + native-wide EXTRA) */
     int active_scale = 1;   /* hi-res mirror used only for 15-bit display */
     bool fmv_frame = false;  /* FMV/boot — present pillarboxed 4:3 in widescreen */
@@ -7017,7 +7017,8 @@ static NetplayVblankEpilogue sdl_vblank_present_body(void) {
         s_disabled_frame_presented = false;
         s_force_present_after_load = false;
         w = di.width; h = di.height;
-        const uint32_t present_h = di.depth24 ? di.screen_height : h;
+        present_h = psx_display_present_height(
+            di.depth24, h, di.screen_height);
         /* 4:3-pinned frames: the pre-game BIOS boot, plus (once engaged) every
          * frame the widescreen layer presents native — FMV video and full-2D
          * menu/title screens. gpu_ws_present_native_43() is the single source
@@ -7259,7 +7260,7 @@ static NetplayVblankEpilogue sdl_vblank_present_body(void) {
      * leave the active image stuck in the upper-left portion of the window. */
 #ifndef PSX_SDL_NO_RENDER
     int src_w = (int)present_w * active_scale;
-    int src_h = (int)h * active_scale;
+    int src_h = (int)present_h * active_scale;
     if (local_viewport_crop_applied && src_w >= 2)
         src_w /= 2;
     if (g_gl_active) {
@@ -7313,8 +7314,8 @@ static NetplayVblankEpilogue sdl_vblank_present_body(void) {
     int dst_h = 480 * tex_scale;
     SDL_Rect dst = { (g_logical_w - dst_w) / 2, 0, dst_w, dst_h };
     /* Match GL: short display bands letterbox inside the 4:3 rect. */
-    if (pin_43 && h > 0 && h < 240) {
-        int content_h = (dst_h * (int)h) / 240;
+    if (pin_43 && present_h > 0 && present_h < 240) {
+        int content_h = (dst_h * (int)present_h) / 240;
         if (content_h < 1) content_h = 1;
         dst.y = (dst_h - content_h) / 2;
         dst.h = content_h;
diff --git a/runtime/tests/test_display_scanout.c b/runtime/tests/test_display_scanout.c
index c774345a..f2d14e65 100644
--- a/runtime/tests/test_display_scanout.c
+++ b/runtime/tests/test_display_scanout.c
@@ -12,6 +12,13 @@ static void test_vertical_offsets(void)
     assert(psx_display_vertical_offset(1, 400, 500) == 0);
 }
 
+static void test_present_height(void)
+{
+    assert(psx_display_present_height(0, 225, 288) == 225);
+    assert(psx_display_present_height(1, 225, 288) == 288);
+    assert(psx_display_present_height(1, 225, 0) == 225);
+}
+
 static void test_vertical_layout(void)
 {
     PsxDisplayVerticalLayout alundra = psx_display_vertical_layout(1, 83, 312);
@@ -36,5 +43,6 @@ int main(void)
 {
     test_vertical_offsets();
     test_vertical_layout();
+    test_present_height();
     return 0;
 }