feat: add screenshot app

programs/src/screenshot/main.cpp

@@ -0,0 +1,168 @@
+/*
+ * main.cpp
+ * MontaukOS Screenshot Tool
+ * Captures the screen framebuffer and saves as JPEG to the user's Pictures directory.
+ * Copyright (c) 2026 Daniel Hammer
+ */
+
+#include <montauk/syscall.h>
+#include <montauk/string.h>
+#include <montauk/heap.h>
+#include <montauk/config.h>
+
+extern "C" {
+#include <string.h>
+#include <stdlib.h>
+#include <stdio.h>
+
+#define STBI_WRITE_NO_STDIO
+#include <gui/stb_image_write.h>
+}
+
+// ============================================================================
+// JPEG write callback - accumulates encoded bytes into a resizable buffer
+// ============================================================================
+
+struct JpegBuffer {
+    uint8_t* data;
+    uint64_t size;
+    uint64_t capacity;
+};
+
+static void jpeg_write_callback(void* context, void* data, int size) {
+    JpegBuffer* buf = (JpegBuffer*)context;
+    if (size <= 0) return;
+
+    uint64_t needed = buf->size + (uint64_t)size;
+    if (needed > buf->capacity) {
+        uint64_t new_cap = buf->capacity * 2;
+        if (new_cap < needed) new_cap = needed;
+        uint8_t* new_data = (uint8_t*)montauk::realloc(buf->data, new_cap);
+        if (!new_data) return;
+        buf->data = new_data;
+        buf->capacity = new_cap;
+    }
+    montauk::memcpy(buf->data + buf->size, data, size);
+    buf->size += (uint64_t)size;
+}
+
+// ============================================================================
+// Entry point
+// ============================================================================
+
+extern "C" void _start() {
+    // Get framebuffer info before doing anything else
+    Montauk::FbInfo fb;
+    montauk::fb_info(&fb);
+
+    int width  = (int)fb.width;
+    int height = (int)fb.height;
+    int pitch  = (int)fb.pitch;
+
+    if (width <= 0 || height <= 0) {
+        montauk::print("screenshot: no framebuffer available\n");
+        montauk::exit(1);
+    }
+
+    // Map the hardware framebuffer (read-only access to screen pixels)
+    uint32_t* hw_fb = (uint32_t*)montauk::fb_map();
+    if (!hw_fb) {
+        montauk::print("screenshot: failed to map framebuffer\n");
+        montauk::exit(1);
+    }
+
+    // Copy framebuffer and convert from BGRA (0xAARRGGBB) to packed RGB
+    uint64_t rgb_size = (uint64_t)width * height * 3;
+    uint8_t* rgb = (uint8_t*)montauk::malloc(rgb_size);
+    if (!rgb) {
+        montauk::print("screenshot: out of memory\n");
+        montauk::exit(1);
+    }
+
+    for (int y = 0; y < height; y++) {
+        uint32_t* src_row = (uint32_t*)((uint8_t*)hw_fb + y * pitch);
+        uint8_t* dst_row = rgb + y * width * 3;
+        for (int x = 0; x < width; x++) {
+            uint32_t px = src_row[x];
+            dst_row[x * 3 + 0] = (px >> 16) & 0xFF; // R
+            dst_row[x * 3 + 1] = (px >> 8)  & 0xFF; // G
+            dst_row[x * 3 + 2] = px & 0xFF;          // B
+        }
+    }
+
+    // Encode as JPEG (quality 100 - maximum quality)
+    JpegBuffer jpeg;
+    jpeg.data = (uint8_t*)montauk::malloc(256 * 1024);
+    jpeg.size = 0;
+    jpeg.capacity = 256 * 1024;
+
+    if (!jpeg.data) {
+        montauk::mfree(rgb);
+        montauk::print("screenshot: out of memory for JPEG buffer\n");
+        montauk::exit(1);
+    }
+
+    int ok = stbi_write_jpg_to_func(jpeg_write_callback, &jpeg,
+                                     width, height, 3, rgb, 100);
+    montauk::mfree(rgb);
+
+    if (!ok || jpeg.size == 0) {
+        montauk::mfree(jpeg.data);
+        montauk::print("screenshot: JPEG encoding failed\n");
+        montauk::exit(1);
+    }
+
+    // Build output path: 0:/users/<username>/Pictures/screenshot_YYYYMMDD_HHMMSS.jpg
+    char username[32] = {};
+    {
+        auto doc = montauk::config::load("session");
+        const char* name = doc.get_string("session.username", "");
+        if (name[0] == '\0') {
+            doc.destroy();
+            montauk::mfree(jpeg.data);
+            montauk::print("screenshot: no user session\n");
+            montauk::exit(1);
+        }
+        montauk::strncpy(username, name, sizeof(username) - 1);
+        doc.destroy();
+    }
+
+    char home[128];
+    snprintf(home, sizeof(home), "0:/users/%s", username);
+
+    // Ensure Pictures directory exists
+    char pictures_dir[192];
+    snprintf(pictures_dir, sizeof(pictures_dir), "%s/Pictures", home);
+    montauk::fmkdir(pictures_dir);
+
+    // Build filename with timestamp
+    Montauk::DateTime dt;
+    montauk::gettime(&dt);
+
+    char filepath[256];
+    snprintf(filepath, sizeof(filepath),
+             "%s/screenshot_%04d%02d%02d_%02d%02d%02d.jpg",
+             pictures_dir,
+             (int)dt.Year, (int)dt.Month, (int)dt.Day,
+             (int)dt.Hour, (int)dt.Minute, (int)dt.Second);
+
+    // Write JPEG file
+    int fd = montauk::fcreate(filepath);
+    if (fd < 0) {
+        montauk::mfree(jpeg.data);
+        montauk::print("screenshot: failed to create file\n");
+        montauk::exit(1);
+    }
+
+    montauk::fwrite(fd, jpeg.data, 0, jpeg.size);
+    montauk::close(fd);
+    montauk::mfree(jpeg.data);
+
+    // Print confirmation
+    char msg[320];
+    snprintf(msg, sizeof(msg), "Screenshot saved: %s (%dx%d, %llu bytes)\n",
+             filepath, width, height, (unsigned long long)jpeg.size);
+    montauk::print(msg);
+
+    montauk::exit(0);
+}