From 125e6177853c28fa5e75e9d3287d6329aebe3181 Mon Sep 17 00:00:00 2001
From: Jim Huang <jserv@ccns.ncku.edu.tw>
Date: Sat, 25 Apr 2026 22:25:08 +0800
Subject: [PATCH] Let no-WM window to match backend dimensions

The fbdev backend was creating a screen using the caller-supplied
dimensions (640x480 from main.c) instead of the actual framebuffer
resolution, causing coordinate space mismatch and clipped rendering
on smaller displays like the STM32F429 Discovery QVGA (320x240).

In no-WM mode, the single window now unconditionally covers the entire
screen rather than merely clamping to it. The screen dimensions are
authoritative and come from the backend -- hardware resolution for
fbdev, window size for SDL, etc.
---
 backend/fbdev.c | 15 ++++++++++++---
 src/window.c    | 20 ++++++++++----------
 2 files changed, 22 insertions(+), 13 deletions(-)

diff --git a/backend/fbdev.c b/backend/fbdev.c
index ff92274..ad5050a 100644
--- a/backend/fbdev.c
+++ b/backend/fbdev.c
@@ -235,7 +235,7 @@ static bool twin_fbdev_work(void *closure)
     return true;
 }
 
-twin_context_t *twin_fbdev_init(int width, int height)
+twin_context_t *twin_fbdev_init(int width maybe_unused, int height maybe_unused)
 {
     char *fbdev_path = getenv(FBDEV_NAME);
     if (!fbdev_path) {
@@ -283,6 +283,15 @@ twin_context_t *twin_fbdev_init(int width, int height)
         goto bail_vt_fd;
     }
 
+    /* Use actual framebuffer resolution instead of caller-supplied dimensions.
+     * The physical display size is authoritative -- the caller's width/height
+     * are only hints suitable for resizable backends like SDL.
+     * Read directly from fb_var which was already validated by
+     * twin_fbdev_apply_config() above -- no redundant ioctl needed.
+     */
+    int fb_width = tx->fb_var.xres;
+    int fb_height = tx->fb_var.yres;
+
     const twin_put_span_t fbdev_put_spans[] = {
         _twin_fbdev_put_span16,
         _twin_fbdev_put_span24,
@@ -290,8 +299,8 @@ twin_context_t *twin_fbdev_init(int width, int height)
     };
     /* Create TWIN screen */
     ctx->screen = twin_screen_create(
-        width, height, NULL, fbdev_put_spans[tx->fb_var.bits_per_pixel / 8 - 2],
-        ctx);
+        fb_width, fb_height, NULL,
+        fbdev_put_spans[tx->fb_var.bits_per_pixel / 8 - 2], ctx);
     if (!ctx->screen) {
         log_error("Failed to create screen");
         goto bail_fb_unmap;
diff --git a/src/window.c b/src/window.c
index 8e31aa9..69c9bac 100644
--- a/src/window.c
+++ b/src/window.c
@@ -63,17 +63,19 @@ twin_window_t *twin_window_create(twin_screen_t *screen,
     width += left + right;
     height += top + bottom;
 #else
-    /* No-WM: ignore position, clamp to screen, no decorations */
+    /* No-WM: the single window always covers the entire screen
+     * regardless of what the application requested.  The screen
+     * dimensions are authoritative -- they come from the backend
+     * (hardware resolution for fbdev, window size for SDL, etc.).
+     */
     left = 0;
     top = 0;
     right = 0;
     bottom = 0;
     x = 0;
     y = 0;
-    if (width > screen->width)
-        width = screen->width;
-    if (height > screen->height)
-        height = screen->height;
+    width = screen->width;
+    height = screen->height;
 #endif
 
     window->client.left = left;
@@ -156,14 +158,12 @@ void twin_window_configure(twin_window_t *window,
 #if defined(CONFIG_WINDOW_MANAGER)
     _twin_window_style_size(style, &border);
 #else
-    /* No-WM: ignore position, clamp to screen, zero margins */
+    /* No-WM: always match the screen provided by the backend. */
     border.left = border.right = border.top = border.bottom = 0;
     x = 0;
     y = 0;
-    if (width > window->screen->width)
-        width = window->screen->width;
-    if (height > window->screen->height)
-        height = window->screen->height;
+    width = window->screen->width;
+    height = window->screen->height;
 #endif
 
     twin_pixmap_disable_update(window->pixmap);