From d2b90bd83ef1d1faa7136fdb6a5db3f4556936b2 Mon Sep 17 00:00:00 2001
From: Scott Duensing <scott@duensing.com>
Date: Mon, 16 Mar 2026 18:10:10 -0500
Subject: [PATCH] Screenshot API added.

---
 dvx/dvxApp.c | 97 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 dvx/dvxApp.h |  6 ++++
 2 files changed, 103 insertions(+)

diff --git a/dvx/dvxApp.c b/dvx/dvxApp.c
index 7ee1df3..e1bfa32 100644
--- a/dvx/dvxApp.c
+++ b/dvx/dvxApp.c
@@ -12,6 +12,8 @@
 #include <dpmi.h>
 #include <signal.h>
 
+#include "thirdparty/stb_image_write.h"
+
 #define DBLCLICK_THRESHOLD     (CLOCKS_PER_SEC / 2)
 #define ICON_REFRESH_INTERVAL  8
 #define KB_MOVE_STEP           8
@@ -24,6 +26,7 @@
 // Prototypes
 // ============================================================
 
+static uint8_t *bufferToRgb(const DisplayT *d, const uint8_t *buf, int32_t w, int32_t h, int32_t pitch);
 static void calcPopupSize(const AppContextT *ctx, const MenuT *menu, int32_t *pw, int32_t *ph);
 static bool checkAccelTable(AppContextT *ctx, WindowT *win, int32_t key, int32_t modifiers);
 static void clickMenuCheckRadio(MenuT *menu, int32_t itemIdx);
@@ -78,6 +81,52 @@ static const char sAltScanToAscii[256] = {
 // calcPopupSize — compute popup width and height for a menu
 // ============================================================
 
+static uint8_t *bufferToRgb(const DisplayT *d, const uint8_t *buf, int32_t w, int32_t h, int32_t pitch) {
+    uint8_t *rgb = (uint8_t *)malloc((size_t)w * h * 3);
+
+    if (!rgb) {
+        return NULL;
+    }
+
+    int32_t bpp = d->format.bytesPerPixel;
+    uint8_t *dst = rgb;
+
+    for (int32_t y = 0; y < h; y++) {
+        const uint8_t *row = buf + y * pitch;
+
+        for (int32_t x = 0; x < w; x++) {
+            uint32_t pixel;
+
+            if (bpp == 1) {
+                pixel = row[x];
+            } else if (bpp == 2) {
+                pixel = ((const uint16_t *)row)[x];
+            } else {
+                pixel = ((const uint32_t *)row)[x];
+            }
+
+            if (d->format.bitsPerPixel == 8) {
+                int32_t idx = pixel & 0xFF;
+                dst[0] = d->palette[idx * 3 + 0];
+                dst[1] = d->palette[idx * 3 + 1];
+                dst[2] = d->palette[idx * 3 + 2];
+            } else {
+                uint32_t rv = (pixel >> d->format.redShift) & ((1u << d->format.redBits) - 1);
+                uint32_t gv = (pixel >> d->format.greenShift) & ((1u << d->format.greenBits) - 1);
+                uint32_t bv = (pixel >> d->format.blueShift) & ((1u << d->format.blueBits) - 1);
+                dst[0] = (uint8_t)(rv << (8 - d->format.redBits));
+                dst[1] = (uint8_t)(gv << (8 - d->format.greenBits));
+                dst[2] = (uint8_t)(bv << (8 - d->format.blueBits));
+            }
+
+            dst += 3;
+        }
+    }
+
+    return rgb;
+}
+
+
 static void calcPopupSize(const AppContextT *ctx, const MenuT *menu, int32_t *pw, int32_t *ph) {
     int32_t maxW     = 0;
     bool    hasSub   = false;
@@ -1389,6 +1438,28 @@ bool dvxUpdate(AppContextT *ctx) {
 }
 
 
+// ============================================================
+// dvxScreenshot
+// ============================================================
+//
+// Save the entire screen (backbuffer) to a PNG file.
+
+int32_t dvxScreenshot(AppContextT *ctx, const char *path) {
+    DisplayT *d = &ctx->display;
+    uint8_t *rgb = bufferToRgb(d, d->backBuf, d->width, d->height, d->pitch);
+
+    if (!rgb) {
+        return -1;
+    }
+
+    int32_t result = stbi_write_png(path, d->width, d->height, 3, rgb, d->width * 3) ? 0 : -1;
+
+    free(rgb);
+
+    return result;
+}
+
+
 // ============================================================
 // dvxShutdown
 // ============================================================
@@ -1421,6 +1492,32 @@ int32_t dvxSetWindowIcon(AppContextT *ctx, WindowT *win, const char *path) {
 }
 
 
+// ============================================================
+// dvxWindowScreenshot
+// ============================================================
+//
+// Save a window's content buffer to a PNG file. This captures the
+// full content area regardless of whether the window is occluded.
+
+int32_t dvxWindowScreenshot(AppContextT *ctx, WindowT *win, const char *path) {
+    if (!win || !win->contentBuf) {
+        return -1;
+    }
+
+    uint8_t *rgb = bufferToRgb(&ctx->display, win->contentBuf, win->contentW, win->contentH, win->contentPitch);
+
+    if (!rgb) {
+        return -1;
+    }
+
+    int32_t result = stbi_write_png(path, win->contentW, win->contentH, 3, rgb, win->contentW * 3) ? 0 : -1;
+
+    free(rgb);
+
+    return result;
+}
+
+
 // ============================================================
 // dvxTileWindows
 // ============================================================
diff --git a/dvx/dvxApp.h b/dvx/dvxApp.h
index c2b1158..43a6bd5 100644
--- a/dvx/dvxApp.h
+++ b/dvx/dvxApp.h
@@ -91,6 +91,9 @@ void dvxMaximizeWindow(AppContextT *ctx, WindowT *win);
 // Request exit from main loop
 void dvxQuit(AppContextT *ctx);
 
+// Save the entire screen to a PNG file (returns 0 on success, -1 on failure)
+int32_t dvxScreenshot(AppContextT *ctx, const char *path);
+
 // Set window title
 void dvxSetTitle(AppContextT *ctx, WindowT *win, const char *title);
 
@@ -109,6 +112,9 @@ const BlitOpsT *dvxGetBlitOps(const AppContextT *ctx);
 // Load an icon for a window from an image file
 int32_t dvxSetWindowIcon(AppContextT *ctx, WindowT *win, const char *path);
 
+// Save a window's content to a PNG file (returns 0 on success, -1 on failure)
+int32_t dvxWindowScreenshot(AppContextT *ctx, WindowT *win, const char *path);
+
 // Create an accelerator table (caller must free with dvxFreeAccelTable)
 AccelTableT *dvxCreateAccelTable(void);