X11 overlay

xoverlay.cpp

/* 
 * Copyright (c) 2020 ericek111 <erik.brocko@letemsvetemapplem.eu>.
 * 
 * This program is free software: you can redistribute it and/or modify  
 * it under the terms of the GNU General Public License as published by  
 * the Free Software Foundation, version 3.
 *
 * This program is distributed in the hope that it will be useful, but 
 * WITHOUT ANY WARRANTY; without even the implied warranty of 
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License 
 * along with this program. If not, see <http://www.gnu.org/licenses/>.
 */

#include <iostream>
#include <stdlib.h>
#include <climits>
#include <chrono>
#include <X11/Xos.h>
#include <X11/Xlib.h>
#include <X11/Xutil.h>
#include <X11/Xatom.h>
#include <X11/extensions/shape.h>
#include <X11/extensions/Xcomposite.h>
#include <X11/extensions/Xfixes.h>
#include <math.h>

// Events for normal windows
#define BASIC_EVENT_MASK (StructureNotifyMask|ExposureMask|PropertyChangeMask|EnterWindowMask|LeaveWindowMask|KeyPressMask|KeyReleaseMask|KeymapStateMask)
#define NOT_PROPAGATE_MASK (KeyPressMask|KeyReleaseMask|ButtonPressMask|ButtonReleaseMask|PointerMotionMask|ButtonMotionMask)

using namespace std;

Display *g_display;
int      g_screen;
Window   g_win;
int      g_disp_width;
int      g_disp_height;
Pixmap   g_bitmap;
Colormap g_colormap;

XColor red;
XColor black;
XColor white;

std::chrono::high_resolution_clock::time_point t1 = std::chrono::high_resolution_clock::now();
std::chrono::high_resolution_clock::time_point t2 = std::chrono::high_resolution_clock::now();
int fpsmeterc = 0;
#define FPSMETERSAMPLE 100
auto duration = std::chrono::duration_cast<std::chrono::microseconds>( t2 - t1 ).count();
string fpsstring = "";

int     shape_event_base;
int     shape_error_base;

// The window size
int WIDTH  = 1920;
int HEIGHT = 1080;

long event_mask = (StructureNotifyMask|ExposureMask|PropertyChangeMask|EnterWindowMask|LeaveWindowMask|KeyRelease | ButtonPress|ButtonRelease|KeymapStateMask);

void allow_input_passthrough (Window w) {
    XserverRegion region = XFixesCreateRegion (g_display, NULL, 0);

    //XFixesSetWindowShapeRegion (g_display, w, ShapeBounding, 0, 0, 0);
    XFixesSetWindowShapeRegion (g_display, w, ShapeInput, 0, 0, region);

    XFixesDestroyRegion (g_display, region);
}

void list_fonts() {
    char **fontlist;
    int num_fonts;
    fontlist = XListFonts (g_display, "*", 1000, &num_fonts);
    for (int i = 0; i < num_fonts; ++i) {
        fprintf(stderr, "> %s\n", fontlist[i]);
    }
}
// Create a XColor from 3 byte tuple (0 - 255, 0 - 255, 0 - 255).
XColor createXColorFromRGB(short red, short green, short blue) {
    XColor color;

    // m_color.red = red * 65535 / 255;
    color.red = (red * 0xFFFF) / 0xFF;
    color.green = (green * 0xFFFF) / 0xFF;
    color.blue = (blue * 0xFFFF) / 0xFF;
    color.flags = DoRed | DoGreen | DoBlue;

    if (!XAllocColor(g_display, DefaultColormap(g_display, g_screen), &color)) {
        std::cerr << "createXColorFromRGB: Cannot create color" << endl;
        exit(-1);
    }
    return color;
}
// Create a XColor from 3 byte tuple (0 - 255, 0 - 255, 0 - 255).
XColor createXColorFromRGBA(short red, short green, short blue, short alpha) {
    XColor color;

    // m_color.red = red * 65535 / 255;
    color.red = (red * 0xFFFF) / 0xFF;
    color.green = (green * 0xFFFF) / 0xFF;
    color.blue = (blue * 0xFFFF) / 0xFF;
    color.flags = DoRed | DoGreen | DoBlue;

    if (!XAllocColor(g_display, DefaultColormap(g_display, g_screen), &color)) {
        std::cerr << "createXColorFromRGB: Cannot create color" << endl;
        exit(-1);
    }

    *(&color.pixel) = ((*(&color.pixel)) & 0x00ffffff) | (alpha << 24);
    return color;
}

// Create a window
void createShapedWindow() {
    XSetWindowAttributes wattr;
    XColor bgcolor = createXColorFromRGBA(0, 0, 0, 0);

    Window root    = DefaultRootWindow(g_display);
    Visual *visual = DefaultVisual(g_display, g_screen);

    XVisualInfo vinfo;
    XMatchVisualInfo(g_display, DefaultScreen(g_display), 32, TrueColor, &vinfo);
    g_colormap = XCreateColormap(g_display, DefaultRootWindow(g_display), vinfo.visual, AllocNone);

    XSetWindowAttributes attr;
    attr.background_pixmap = None;
    attr.background_pixel = bgcolor.pixel;
    attr.border_pixel=0;
    attr.win_gravity=NorthWestGravity;
    attr.bit_gravity=ForgetGravity;
    attr.save_under=1;
    attr.event_mask=BASIC_EVENT_MASK;
    attr.do_not_propagate_mask=NOT_PROPAGATE_MASK;
    attr.override_redirect=1; // OpenGL > 0
    attr.colormap = g_colormap;

    //unsigned long mask = CWBackPixel|CWBorderPixel|CWWinGravity|CWBitGravity|CWSaveUnder|CWEventMask|CWDontPropagate|CWOverrideRedirect;
    unsigned long mask = CWColormap | CWBorderPixel | CWBackPixel | CWEventMask | CWWinGravity|CWBitGravity | CWSaveUnder | CWDontPropagate | CWOverrideRedirect;

    g_win = XCreateWindow(g_display, root, 0, 0, WIDTH, HEIGHT, 0, vinfo.depth, InputOutput, vinfo.visual, mask, &attr);

	g_bitmap = XCreateBitmapFromData (g_display, RootWindow(g_display, g_screen), (char *)myshape_bits, myshape_width, myshape_height);

    //XShapeCombineMask(g_display, g_win, ShapeBounding, 900, 500, g_bitmap, ShapeSet);
    XShapeCombineMask(g_display, g_win, ShapeInput, 0, 0, None, ShapeSet );

    // We want shape-changed event too
    #define SHAPE_MASK ShapeNotifyMask
    XShapeSelectInput (g_display, g_win, SHAPE_MASK );

    // Tell the Window Manager not to draw window borders (frame) or title.
	wattr.override_redirect = 1;
    XChangeWindowAttributes(g_display, g_win, CWOverrideRedirect, &wattr);
    allow_input_passthrough(g_win);

    // Show the window
    XMapWindow(g_display, g_win);

    red = createXColorFromRGBA(255, 0, 0, 255);
    black = createXColorFromRGBA(0, 0, 0, 200);
    white = createXColorFromRGBA(255, 255, 255, 255);
}


// Draw on the shaped window.
// Yes it's possible, but only pixels that hits the mask are visible.
// A hint: You can change the mask during runtime if you like.
void draw()
{
    fpsmeterc++;
    if(fpsmeterc == FPSMETERSAMPLE) {
        fpsmeterc = 0;
        t1 = t2;
        t2 = std::chrono::high_resolution_clock::now();
        duration = std::chrono::duration_cast<std::chrono::microseconds>( t2 - t1 ).count();
        fpsstring = /*to_string(duration) + " / " +*/ to_string(1000000*FPSMETERSAMPLE/duration);
    }


    GC gc;
    XGCValues gcv;

    /*// Line width and type
    gcv.line_width = 1;
    gcv.line_style = LineSolid;
    gcv.foreground = red.pixel;

    unsigned long mask = GCLineWidth | GCLineStyle | GCForeground;
    gc = XCreateGC(g_display, g_win, mask, &gcv);*/
    
    gc = XCreateGC (g_display, g_win, 0, 0);
    XSetBackground (g_display, gc, white.pixel); 
    XSetForeground (g_display, gc, red.pixel);

    XFontStruct * font;
    // const char * fontname = "-misc-fixed-bold-r-normal--18-120-100-100-c-90-iso8859-2";
    // const char * fontname = "rk24"; // ~ chinese shit
    // list_fonts(); 

    const char * fontname = "9x15bold";
    font = XLoadQueryFont (g_display, fontname);
    /* If the font could not be loaded, revert to the "fixed" font. */
    if (!font) {
        fprintf (stderr, "unable to load font %s > using fixed\n", fontname);
        font = XLoadQueryFont (g_display, "fixed");
    }
    XSetFont (g_display, gc, font->fid);

    XSetForeground (g_display, gc, black.pixel);
    XFillRectangle(g_display, g_win, gc, 0, 0, 250, 30);

    XSetForeground (g_display, gc, red.pixel);
    if(duration > 0.0f) {
        const char * text = fpsstring.c_str();
        XDrawString(g_display, g_win, gc, 10, 20, text, strlen(text));
    }

    XFreeGC(g_display, gc);

}

void openDisplay() {
    g_display = XOpenDisplay(0);

    if (!g_display) {
        cerr << "Failed to open X display" << endl;
        exit(-1);
    }

    g_screen    = DefaultScreen(g_display);

    g_disp_width  = DisplayWidth(g_display, g_screen);
    g_disp_height = DisplayHeight(g_display, g_screen);

    // Has shape extions?
    if (!XShapeQueryExtension (g_display, &shape_event_base, &shape_error_base)) {
       cerr << "NO shape extension in your system !" << endl;
       exit (-1);
    }
}


int main() {
    openDisplay();

    createShapedWindow();

    XEvent xevt;
    XExposeEvent *eev;
    XConfigureEvent *cev;
    XKeyEvent *kev;

    while (1)
    {
        /*XNextEvent(g_display, &xevt);

        // Note!  Shaped window generates some special events
        // You got "shape_event_base" from XShapeQueryExtension(...)
        if (xevt.type == shape_event_base + ShapeNotify)
        {
            cout << "Got shape changed event" << endl;
            continue;
        }

        switch (xevt.type)
        {
        case Expose:
            if (xevt.xexpose.count != 0) continue;
            eev = &xevt.xexpose;

            draw();
            break;

        case KeyPress:
            kev = &xevt.xkey;
            exit(0);
            break;

        case ConfigureNotify:
            cev = &xevt.xconfigure;
            break;

        }*/

        draw();
        usleep(1000);
    }

    return 0;
}

@ericek111 hi, would you be interested in adding an open-source license to this code? I'd like to base a project off this program, but without a license I can't legally do that.

Hey. Thanks for respecting the spirit of open-source! I've licensed the code under GPLv3. If that does not suit you, we can arrange something else, though GPL is preferred.

Awesome, thanks! GPL is fine.

xdrawoverlay.c: In function ‘void createShapedWindow()’:
xdrawoverlay.c:145:88: error: ‘myshape_bits’ was not declared in this scope
145 | g_bitmap = XCreateBitmapFromData (g_display, RootWindow(g_display, g_screen), (char *)myshape_bits, myshape_width, myshape_height);
| ^~~~~~~~~~~~
xdrawoverlay.c:145:102: error: ‘myshape_width’ was not declared in this scope
145 | g_bitmap = XCreateBitmapFromData (g_display, RootWindow(g_display, g_screen), (char *)myshape_bits, myshape_width, myshape_height);
| ^~~~~~~~~~~~~
xdrawoverlay.c:145:117: error: ‘myshape_height’ was not declared in this scope
145 | g_bitmap = XCreateBitmapFromData (g_display, RootWindow(g_display, g_screen), (char *)myshape_bits, myshape_width, myshape_height);
| ^~~~~~~~~~~~~~

@liangqi g_bitmap is not used anywhere, so you can remove lines 145 and 41 without problem, then compile with

g++ overlay.cpp -o overlay -lX11 -lXext -lm -lXfixes

Thanks for a very helpful example. I think before line 221 (XFreeGC()) you need:

XFreeFont(g_display, font);

to avoid leaking the font each time the draw loop is called.

This has been extremely useful. I need an external overlay for a program I'm making, and it has been almost impossible to make a X window which does exactly this.
I'd give it a star if it wasn't a gist.

In case anyone is interested, here is a C fork with some extra stuff: Link.