generate screenshot using Xlib.

internal/desktop/xorg/xorg.c

@@ -136,3 +136,33 @@ XFixesCursorImage *XGetCursorImage(void) {
   Display *display = getXDisplay();
   return XFixesGetCursorImage(display);
 }
+
+char *XGetScreenshot(int *w, int *h) {
+  Display *display = getXDisplay();
+  Window root = DefaultRootWindow(display);
+
+  XWindowAttributes attr;
+  XGetWindowAttributes(display, root, &attr);
+  int width = attr.width;
+  int height = attr.height;
+
+  XImage *ximage = XGetImage(display, root, 0, 0, width, height, AllPlanes, ZPixmap);
+
+  *w = width;
+  *h = height;
+  char *pixels = (char *)malloc(width * height * 3);
+
+	for (int row = 0; row < height; row++) {
+		for (int col = 0; col < width; col++) {
+			int pos = ((row * width) + col) * 3;
+      unsigned long pixel = XGetPixel(ximage, col, row);
+
+			pixels[pos]   = (pixel & ximage->red_mask)   >> 16;
+			pixels[pos+1] = (pixel & ximage->green_mask) >> 8;
+			pixels[pos+2] =  pixel & ximage->blue_mask;
+    }
+  }
+
+  XDestroyImage(ximage);
+  return pixels;
+}

internal/desktop/xorg/xorg.go

@@ -13,6 +13,9 @@ import (
 	"time"
 	"unsafe"
 
+	"image"
+	"image/color"
+
 	"demodesk/neko/internal/types"
 )
 
@@ -244,6 +247,34 @@ func GetCursorImage() *types.CursorImage {
 	}
 }
 
+func GetScreenshotImage() *image.RGBA {
+	mu.Lock()
+	defer mu.Unlock()
+
+	var w, h C.int
+	pixelsUnsafe := C.XGetScreenshot(&w, &h)
+	pixels := C.GoBytes(unsafe.Pointer(pixelsUnsafe), w * h * 3)
+	defer C.free(unsafe.Pointer(pixelsUnsafe))
+
+	width := int(w)
+	height := int(h)
+	img := image.NewRGBA(image.Rect(0, 0, width, height))
+	for row := 0; row < height; row++ {
+		for col := 0; col < width; col++ {
+			pos := ((row * width) + col) * 3
+
+			img.SetRGBA(col, row, color.RGBA{
+				R: uint8(pixels[pos]),
+				G: uint8(pixels[pos+1]),
+				B: uint8(pixels[pos+2]),
+				A: 0xFF,
+			})
+		}
+	}
+
+	return img
+}
+
 //export goCreateScreenSize
 func goCreateScreenSize(index C.int, width C.int, height C.int, mwidth C.int, mheight C.int) {
 	ScreenConfigurations[int(index)] = types.ScreenConfiguration{

internal/desktop/xorg/xorg.h

@@ -2,6 +2,7 @@
 
 #include <X11/Xlib.h>
 #include <X11/XKBlib.h>
+#include <X11/Xutil.h>
 #include <X11/extensions/Xrandr.h>
 #include <X11/extensions/XTest.h>
 #include <X11/extensions/Xfixes.h>
@@ -27,3 +28,5 @@ short XGetScreenRate();
 void XSetKeyboardModifier(int mod, int on);
 char XGetKeyboardModifiers();
 XFixesCursorImage *XGetCursorImage(void);
+
+char *XGetScreenshot(int *w, int *h);