I am trying to make an application which will graphically repeat the mouse pointer, so I can ultimately make a mouse trail program, for Ubuntu 18.04 - and it seems, the way to do it is via X11/Xlib - although, these days I don't even know, as my machine says also wayland:
$ loginctl | while IFS= read line; do echo "$line"; if [[ $line == *"tty"* ]]; then sessnum=$(echo "$line" | awk '{print $1;}'); echo sessnum: $sessnum\; $(loginctl show-session $sessnum -p Type); fi; done
SESSION UID USER SEAT TTY
c1 121 gdm seat0 tty1
sessnum: c1; Type=wayland
2 1000 administrator seat0 tty2
sessnum: 2; Type=x11
2 sessions listed.
Regardless, I managed to put together an unholy assemblage of:
https://keithp.com/blogs/Cursor_tracking/ - which sets up the program for capturing raw mouse events, so the mouse pointer position can be extracted (and a redraw triggered) whenever the mouse pointer position changes
xosd.c (via https://github.com/AndreRenaud/XOSD) - I thought at first that On-Screen Display would have a special method to draw on top - but this sets up a topmost window, child of the root, where all drawing happens; and it also sets up event and timer thread
.... plus a ton of other code snippets (mostly from SO), which sort of does what I want (even if I don't really fully understand all of the layers and compositing that goes on in it). I posted this as a gist: xosd_track_cursor.c since it's 700+ lines (but can post it here if needed).
Here is how the application behaves (also see full-res imgur .mp4 video)
Basically, at start, the "OSD" topmost window is set up, and it's quite smaller than the desktop window - which helps us see the window border decorations around it (ultimately, I'd make this window the same size as the desktop).
At start, the desktop pixels at the location of this window have seemingly been copied as the window background.
Once the mouse pointer enters the OSD window, there is a draw of a circle, which becomes the mask for the OSD window (which again can be seen via the window border decorations) - and this circular window follows the mouse. Then, inside it, I draw a XFillRectangle to draw a lime rectangle, and then XPutImage to draw the pixels captured from the latest mouse pointer (the video doesn't show it, but also the copied cursor changed when the normal one does, say from left_ptr to bottom_side or xterm cursor bitmaps).
So far so good - but these are the problems, and questions:
All of the draws - both the lime rectangle and the mouse pointer copy - remain on the OSD window, and are not cleared upon redraw (which is quite obvious when the mouse pointer leaves the OSD window, so there is no masking). How can I erase these previous draws each time a new state is rendered?
When I click on window to change the focus, it is obvious (especially when the mouse pointer leaves the OSD window, so there is no masking) that the desktop "background" shown in the OSD window, shows the state when the program started. How can I capture the current state of the desktop background (that is, behind the OSD window), so I can use that for clearing the OSD window in the previous step?
(I thought I could hide the OSD window, then capture the desktop at the same location with XGetImage, maybe (?) - then show the window; but show always sends Expose event, which otherwise runs the expose function that does the redraw, and so I get a bunch of recursive calls hogging the application)
The mouse pointer copy is rendered with a black background - how can I make the drawing of mouse pointer copy transparent, where it is black now?
And, a sort of a bonus question (just curious here - obviously I'd rather not have the leftovers to begin with):
I first do XFillRectangle to draw a lime rectangle, then XPutImage to draw the pixels of the mouse pointer copy. I'd expect this to show the mouse cursor copy on top of the green pixels - and it is indeed so, while the OSD window is masked with the circle. But when the OSD window is shown in full, the leftovers make it seem as if the green pixels were drawn on top of the mouse cursor copy pixels. Why is this so?
Well, I think I got somewhere - the result is in the same gist, just different revision: gist: xosd_track_cursor.c (a31e9dff5); and it looks like this:
And so, to answer my questions:
How can I erase these previous draws each time a new state is rendered?
Cannot - not in the way the previous code was set up. It was set up as a override_redirect, meaning it would stay out of the management of any window manager. Furthermore, the default bit depth was 24, meaning that transparency was not supported, meaning that to grab the desktop "behind" (to use as "clear" background), we'd had to hide and then show the window, which used to cause recursion due to reaction to Expose events.
However, I saw in How to make an OpenGL rendering context with transparent background? that using an glXCreateContext might help - and it did. However, it turns out, it was not necessary - as soon as XMatchVisualInfo successfully returned a match for 32-bit depth for the OSD window (alpha transparency supported), then it was possible to define a "fully transparent" color, via XSetForeground, as 0x00000000 (as far as I see, that is 0xAARRGGBB format) - and use that to draw directly on the window with XFillRectangle -> that manages to clear the entire OSD window transparently.
The mouse pointer copy is rendered with a black background - how can I make the drawing of mouse pointer copy transparent, where it is black now?
Turns out, also this started working as soon as the window was created with XCreateWindow using settings from XMatchVisualInfo for 32-bit depth. By that, I mean that the result of XPutImage was such, that the transparent points in the cursor image were now "see-through"/transparent - whereas previously, the result of XPutImage showed black pixels at those locations.
But when the OSD window is shown in full, the leftovers make it seem as if the green pixels were drawn on top of the mouse cursor copy pixels. Why is this so?
Apparently, I didn't remember correctly what order the pixels were drawn in; when that demo capture was taken, indeed the mouse cursor pixels were copied first, and then the green pixels were copied on top. ( which now changes the question - how come the mouse cursor was visible in that capture, at all?! but now that the overall problem is solved, I'm not that curious :) )
Otherwise, few more notes on gist: xosd_track_cursor.c (a31e9dff5): since X11 has a client/server architecture, that means the user program can only queue requests to the server, and thus all of the drawing calls are asynchronous/non-blocking - and so, when we run, say, XFillRectangle and it exits, it does not mean that the drawing of pixels has been finished - just that the request has been sent to the queue, that ends up being sent to the server. Furthermore, in spite of commands like XFlush, XSync - there is never a guarantee that we can wait for a finished drawing operation; and there is no guarantee either that the server will honor any given request.
However, the less you try to do, the bigger the probability the X Server will honor the requests. So this version of the code actually makes a smallish window, 60x60 pixels, then sets it up so it is (centrally aligned) dragged by the motion of the mouse pointer. Then, the (main) mouse pointer is simply copied in this window at the same relative location.
Finally, there is a primitive attempt to do a mouse trail, by rendering two "ghost" copies of the mouse pointer, and have them be displaced by a history of mouse motion delta vector - the effect, as is visible on the gif, is not really amazing, but at least it's there as a "proof of concept", of sorts. Also, the window is setup at start as "click-through" using XShapeCombineRectangles - meaning the OSD window doesn't pick up/handle any mouse events (clicks) directly on it, instead everything is automatically passed to the windows below it, so the interaction remains the same, as if the program was not running at all.
(Note that to get the behavior of gist: xosd_track_cursor.c (a31e9dff5) shown in the gif, you should look up the defines DEBUGPRINT and MOUSE_TRAIL, and have them uncommented when you build)
I noticed that when our WPF application’s GUI thread is stuck for a few seconds, the application’s main window moves a few pixels to the top and left, and then, when the GUI thread is freed, the window returns to its location.
I also noticed it happen in Visual Studio when I save a complex file and CodeMaid is busy cleaning it – Visual Studio window moves a few pixels to the top and left, and then, when the job is done, it returns to its previous location.
This doesn’t always happen and is not easily reproducible. It seems not to happen when the window is maximized.
Can anyone say why this happens, and, more important, how to avoid it (other than keeping the GUI thread from getting stuck…)?
Ive been googling this alot but can't find any working solution. Im using Shell Integration Library to cerate custom Window Chrome and I also need drop shadows for this window. Some say setting GlassFrameThickness to -1 do the trick but its not working for me. And Jeremiah Morrill suggested using DwmExtendFrameIntoClientArea. Ive tried that and it works, sort of. The shadows looks ok but when the window is shown it is first shown as a glass-frame and then a second later the real content is superimposed. This causes to much flickering for me. Is there any way to get rid of this flickering or is there any better way using only Shell Integration Library?
I had a similar problem where it wouldn't display any shadow when using a custom chrome. It worked fine when using the glass.
I got a shadow by setting GlassFrameThickness="0,0,0,1". The glass didn't show and I got the shadow.
Be warned, the shadow is a simple RECT to Windows, so if you have a funky chrome with transparencies it may look funny.
Also if you support the maximized state be aware the you'll need to set a margin on your top-level panel element of "8,8,8,8" when in maximized mode. All other modes should be "0,0,0,0".
To alimbada, the WindowStyle defaults to None on custom chrome.
The Shell Integration Library uses DwmExtendFrameIntoClientArea, plus handling of several Window messages to get the effects. If you're using the full window rect (i.e. no rounded corners) then setting it to (0,0,0,1) as suggested will give you the drop shadows as you want. If you want to simulate the rounded corners of Aero, then setting it to (8,8,8,8) will extend the glass frame enough that the corners also stay rounded, and then you're responsible for not drawing over the corners of the rectangle. The shape of the drop shadow doesn't change regardless of the glass frame thickness.
The flashing you're seeing when setting the thickness to -1 still exists even when not fully extending the glass frame. What's happening is the window is getting shown while the content is still compositing. What you can do is simplify the default UI so it displays quicker (or you can stage it, bringing in a simnple background first and then replacing it with something usable), or you can create and show the window off-screen, and then move it to the desired start location once the content has been rendered. The easy way to detect when it's probably ready is to invoke a DispatchTimer with Priority=Loaded. That should only get invoked once the basic first layout has been completed.
I cannot not find any way to restore the Saved Window Position without seeing the Window jump from its initial default Position to the Restored Position. The problem is that the first time I get access to the Window its already visible to the user. Am I missing something or is there currently no way to do this?
Try adjusting OOB Settings, Width=1, Height=1
It is not ideal, but tolerable.
The window opens very small, then resizes correctly.
I also found that when restoring the window position, you have to set the Width and Height first, then Top and Left. Otherwise there appears to be a bug which sometimes resets the top or left.
I have a rather basic shell of a WPF app that I am creating. When I move it using the DragMove() function the app moves properly but seems to "jerk" a lot. It seems to me that the redraw rate is very low making the application look slow and unresponsive.
Currently there is no "code" besides a call to DragMove().
The XAML consists of an outer border with rounded corners and drop shadow set to RenderingBias="Performance". There is also a small gradient on the title bar and a path. But even commenting these out of the code still makes the app appear jerky and slow whilst moving.
Note I have ran this in Release and outside the debugger too.
From experience, try removing the drop shadow and you'll see much better perfomance.
http://social.msdn.microsoft.com/Forums/en-US/wpf/thread/99faecec-395f-4a47-92ee-620b11c39ae7