Rectangle is flickering while dragging on screen with xlib Post: 302907014

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Special Forums UNIX and Linux Applications Rectangle is flickering while dragging on screen with xlib Post 302907014 by whatnext on Wednesday 25th of June 2014 10:01:25 AM

06-25-2014

Registered User

Rectangle is flickering while dragging on screen with xlib

Hi, this is my first post here.

I wanto make a screencasting program. I want to make a screen part selection to grab coordinates of the screen location.
I found a nice prototype

Code:

#include <X11/Xlib.h>
//#include <X11/Xresource.h>

#include <stdlib.h>
#include <stdio.h>
#include <string.h>

int main()
{
    Display *dpy;
    XEvent ev;

    GC sel_gc;
    XGCValues sel_gv;

    int x, y, i;
    int start_x, start_y, width, height;


    if (!(dpy = XOpenDisplay(NULL))) {
        fprintf(stderr, "Could not open display %s", getenv("DISPLAY"));
    }

    XGrabButton(dpy, 1, 0, DefaultRootWindow(dpy), True, ButtonPressMask, GrabModeSync, GrabModeAsync, None, None);

    sel_gv.function = GXinvert;
    sel_gv.subwindow_mode = IncludeInferiors;
    sel_gv.line_width = 1;
    sel_gc = XCreateGC(dpy, DefaultRootWindow(dpy), GCFunction | GCSubwindowMode | GCLineWidth, &sel_gv);

    for (;;) {
        XNextEvent(dpy, &ev);

        if (ev.type == ButtonPress) {
            /* Grab pointer so we receive ButtonRelease */
            XGrabPointer(dpy, DefaultRootWindow(dpy), True, PointerMotionMask | ButtonReleaseMask, GrabModeAsync, GrabModeAsync, None, None, CurrentTime);
            x = start_x = ev.xbutton.x_root;
            y = start_y = ev.xbutton.y_root;

            width = height = 0;

            //XAllowEvents(dpy, ReplayPointer, CurrentTime); /* Allow other apps to process this message */
        } else if (ev.type == MotionNotify) {
            while (XCheckTypedEvent(dpy, MotionNotify, &ev));

            XDrawRectangle(dpy, DefaultRootWindow(dpy), sel_gc, x, y, width, height); /* Clear Rectangle */

            width = ev.xbutton.x_root - start_x;
            height = ev.xbutton.y_root - start_y;

            /* Ugliness to make width/height positive and put the start positions
             * in the right place so we can draw backwards basically. */
            if (width < 0) { width = abs(width); x = ev.xbutton.x_root; } else { x = start_x; }
            if (height < 0) { height = abs(height); y = ev.xbutton.y_root; } else { y = start_y; }

            XDrawRectangle(dpy, DefaultRootWindow(dpy), sel_gc, x, y, width, height); /* Draw Rectangle */
        } else if (ev.type == ButtonRelease) {
            XUngrabPointer(dpy, CurrentTime);

            XDrawRectangle(dpy, DefaultRootWindow(dpy), sel_gc, x, y, width, height); /* Clear Rectangle */

            XSync(dpy, 1); /* Needed to Ungrab Pointer NOW otherwise we continue receiving MotionNotify events and the previous line is useless */

            printf("%i %i %i %i\n", x, y, width, height);
        }
    }

    XFreeGC(dpy, sel_gc);

    XCloseDisplay(dpy);

    return 0;
}

I am on Ubuntu 14.04 platform, I compiled and run the code. While dragging mouse I get flickering and partially missing rectangle. I wonder if it's specific to my system or xlib library deprecated?

Would anybody here help me fix it please?

whatnext

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xshapecombineshape

XSHAPE(3X11)							    X FUNCTIONS 						      XSHAPE(3X11)

NAME

       XShapeQueryExtension,  XShapeQueryVersion,  XShapeCombineRegion, XShapeCombineRectangles, XShapeCombineMask, XShapeCombineShape, XShapeOff-
       setShape, XShapeQueryExtents, XShapeSelectInput, XShapeInputSelected, XShapeGetRectangles - X nonrectangular shape functions

SYNTAX

       #include <X11/extensions/shape.h>

       Bool XShapeQueryExtension (
	    Display *dpy,
	    int *event_basep,
	    int *error_basep);

       Status XShapeQueryVersion (
	    Display *dpy,
	    int *major_versionp,
	    int *minor_versionp);

       void XShapeCombineRegion (
	    Display *dpy,
	    Window dest,
	    int destKind,
	    int xOff,
	    int yOff,
	    struct _XRegion *r,
	    int op);

       void XShapeCombineRectangles (
	    Display *dpy,
	    XID dest,
	    int destKind,
	    int xOff,
	    int yOff,
	    XRectangle *rects,
	    int n_rects,
	    int op,
	    int ordering);

       void XShapeCombineMask (
	    Display *dpy,
	    XID dest,
	    int destKind,
	    int xOff,
	    int yOff,
	    Pixmap src,
	    int op);

       void XShapeCombineShape (
	    Display *dpy,
	    XID dest,
	    int destKind,
	    int xOff,
	    int yOff,
	    Pixmap src,
	    int srcKind,
	    int op);

       void XShapeOffsetShape (
	    Display *dpy,
	    XID dest,
	    int destKind,
	    int xOff,
	    int yOff);

       Status XShapeQueryExtents (
	    Display *dpy,
	    Window window,
	    int *bShaped,
	    int *xbs,
	    int *ybs,
	    unsigned int *wbs,
	    unsigned int *hbs,
	    int *cShaped,
	    int *xcs,
	    int *ycs,
	    unsigned int *wcs,
	    unsigned int *hcs);

       void XShapeSelectInput (
	    Display *dpy,
	    Window window,
	    unsigned longmask);

       unsigned long XShapeInputSelected (
	    Display *dpy,
	    Window window);

       XRectangle *XShapeGetRectangles (
	    Display *dpy,
	    Window window,
	    int kind,
	    int *count,
	    int *ordering);

STRUCTURES

       typedef struct {
	   int type;
	   unsigned long serial;
	   Bool send_event;
	   Display *display;
	   Window window;
	   int kind;
	   int x, y;
	   unsigned width, height;
	   Time time;
	   Bool shaped;
       } XShapeEvent;

DESCRIPTION

       The X11 Nonrectangular Window Shape Extension adds nonrectangular windows to the X Window System.

PREDEFINED VALUES

       Operations:
	    ShapeSet
	    ShapeUnion
	    ShapeIntersect
	    ShapeSubtract
	    ShapeInvert

       Shape Kinds:
	    ShapeBounding
	    ShapeClip

       Event defines:
	    ShapeNotifyMask
	    ShapeNotify

BUGS

       This manual pages needs a lot more work.

SEE ALSO

       X11 Nonrectangular Window Shape Extension

X Version 11							    Release 6.6 						      XSHAPE(3X11)

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