How to differentiate between repaint
A repaint occurs when changes are made to elements that affect
visibility but not the layout. For example, opacity, background-color,
visibility, and outline. Repaints are expensive because the browser
must check the visibility of all other nodes in the DOM — one or more
may have become visible beneath the changed element.
and reflow
Reflows have a bigger impact. This refers to the re-calculation of
positions and dimensions of all elements, which leads to re-rendering
part or all of the document. Changing a single element can affect all
children, ancestors, and siblings.
using chrome developer tools(or other similar tools)?
In Chrome Performance tab i see only repaint.
repaint
Related
Recently I read this description of the browser repaint process:
A repaint occurs when changes are made to elements that affect visibility but not the layout. For example, opacity, background-color, visibility, and outline. Repaints are expensive because the browser must check the visibility of all other nodes in the DOM — one or more may have become visible beneath the changed element.
I was a little surprised by the last sentence. Why must a (Webkit-based) browser re-check the visibility of all nodes in the render tree for any and every repaint? Even of an item in its own render layer?
I would like to draw some sort of window on top of all the other windows. For example, to display some debugging infos (like conky) or things like a timer.
The main thing is that I would like to able to continue using the other windows while using it (the events go through transparently).
I've tried doing it with pygtk, pyqt and others but can't find a way to make it a real overlay with no event capture.
Is there some low-level x11 solution?
I think the Composite-extension-approach will not work when a compositing manager is running (and thus Composite's overlay window is already used).
Since you explicitly mention "no event capture":
The SHAPE extension allows to set some different shapes for a window. Version 1.1 of this extension added the "input" shape. Just setting this to an empty region should pretty much do what you want.
Some concrete example of exactly what I think you ask for can be found in Conky's source code: http://sources.debian.net/src/conky/1.10.3-1/src/x11.cc/?hl=769#L764-L781
Edit: Since you said that you didn't find anything in Gtk (well, PyGtk), here is the function that you need in Gtk: https://developer.gnome.org/gdk3/stable/gdk3-Windows.html#gdk-window-input-shape-combine-region
You might need Composite extension + GetOverlayWindow request:
Version 0.3 of the protocol adds the Composite Overlay Window, which
provides compositing managers with a surface on which to draw without
interference. This window is always above normal windows and is always
below the screen saver window. It is an InputOutput window whose width
and height are the screen dimensions. Its visual is the root visual
and its border width is zero. Attempts to redirect it using the
composite extension are ignored. This window does not appear in the
reply of the QueryTree request. It is also an override redirect
window. These last two features make it invisible to window managers
and other X11 clients. The only way to access the XID of this window
is via the CompositeGetOverlayWindow request. Initially, the Composite
Overlay Window is unmapped.
CompositeGetOverlayWindow returns the XID of the Composite Overlay
Window. If the window has not yet been mapped, it is mapped by this
request. When all clients who have called this request have terminated
their X11 connections the window is unmapped.
Composite managers may render directly to the Composite Overlay
Window, or they may reparent other windows to be children of this
window and render to these. Multiple clients may render to the
Composite Overlay Window, create child windows of it, reshape it, and
redefine its input region, but the specific arbitration rules followed
by these clients is not defined by this specification; these policies
should be defined by the clients themselves.
C api : XCompositeGetOverlayWindow
PyGTK Solution:
I think the composite and shapes X extensions are sufficiently ubiquitous and shall assume here that they are active on your system. Here's PyGtk code for this:
# avoid title bar and standard window minimize, maximize, close buttons
win.set_decorated(False)
# make the window stick above all others (super button will still override it in the z-order, which is fine)
win.set_keep_above(True)
# make events pass through
region = cairo.Region(cairo.RectangleInt(0, 0, 0, 0))
my_window.input_shape_combine_region(region)
win.show_all()
# set the entire window to be semi-transparent, if we like
win.set_opacity(0.2)
Basically what this does is tell Gtk that other than pixel (0,0) the entire window my_window should not be considered part of itself in terms of event propagation. That in turn, according to my current understanding means that when the pointer moves and clicks, the events go to the underlying window under the pointer position, as if my_window was not there.
Caveat:
This does allow your overlay window being the focus window (due to user-solicited window switching or just because it pops up and gets the focus when your application starts). Which means that for example, keyboard events will still undesirably go to it up until the user has clicked through it to make it lose focus in favor of whatever window is under the cursor. I would likely use the approach described here to iron out this aspect.
If there's a different and proper approach for making a portion of the screen "display stuff but not receive events", without building an oddball window like above over it, I'm happy to learn about it.
I assume that one's particular desktop environment (gnome, unity, etc. on linux) may interfere with this solution depending on version and configuration, on some occasions.
I've created a nav menu like in the screenshot below. It spans the entire width of the container and the left/right padding of each menu item is constant. This was easy to do by hardcoding the left/right padding in the CSS, but I want the paddings to be able to change as the site admin edits the menus.
Is there a way to do this with pure CSS (CSS3 is okay)?
This was easy enough to do with jQuery (I totaled up the width of the menu items and calculated the necessary padding). But I ran into some issues on some browsers due to our use of Google Web Fonts. On Chrome and Firefox 4 on Windows (not on Mac), the web font was not loaded at the time that my script ran, resulting in incorrect width measurements. I tried running the script in the jQuery's DOM ready event and in the Google Font API's active event. The active event worked in Chrome but in Firefox 4 it was often fired before the font had been applied.
Thanks in advance.
Here's a jsfiddle of a potential different solution.
Using that layout, and assuming the number of menu items is going to change, you call a recalculation method once a list item is added/removed. In this example provided, I've used YUI3 to do the DOM manipulation, but you could do that a number of ways. Note - I didn't test the javascript function, its "probably working pseudo code".
(You may need to make subtract a further 2% or so from the list item widths, if you're trying to deal with IE6/7)
Use jQuery's .load event as suggested by user thirtydot.
I have a grid/canvas that has an element (say an icon with an image and text overlayed) added to it dynamically via code.
Most of the time it renders correctly when added (content is aligned properly inside it),
but sometimes all the content sits in one corner.
I can remove/add/remove/add/remove/add and it will eventually do it
After a movement of the parent canvas, the element corrects itself as if the layout has been updated.
I have tried the following on Loaded and OnApplyTemplate for both the element and the element parent but it still seems to happen occasionally
InvalidateMeasure()
InvalidateArrange()
UpdateLayout()
Any ideas on why the content wouldn't arrange would be appreciated cause its driving me nuts
I'm not sure why it works for you sometimes but not others. But a grid has the inherent ability to dynamically resize itself and its contents. A canvas doesn't (you'd have to handle that manually in code).
If you change your canvas to a grid does it work? A grid has slightly more overhead than a canvas but it sounds to me like you need its functionality anyway.
I have several nested X Windows - let's say - a scrollable window within a scrollable window (see the example below). In such case the main window contains (at least) the major scroll bars and the (major) drawing area they control. This drawing area on its turn contains (at least) a scrollable window batch - a (minor) main window, containing a scroll bar and minor drawing area.
During live scrolling of an inner drawing area the redraw procedure messes up, because I am using the XCopyArea to speed the process and move the contents that are valid and invoke the actual redraw routine for just the newly appeared content. This works fine when the inner drawing batch is by itself, but when nested within another one a problem occurs - when the inner scrolling-batck is partially visible (i.e. the major drawing area is scrolled) redrawing of newly appeared contents is clipped from the major drawing area and never actually redrawn, but considered to be so. When on the next scroll XCopyArea gets this supposedly-redrawn area it is actually empty. Finally this empty area show up on the partially visible inner scrolling-batch and it is empty. On the first general redraw message they are fixed.
If I can obtain the clipping mask for what is actually visible from (my) inner drawing area I can adjust the XCopyArea() call and redraw call and overcome the problem without the plan "B" which is redrawing all contents on each scroll bar movement.
Example: Developing a plugin for Mozilla Firefox and needing to determine the region that describes the visible area of "my" window, i.e. the one that is passed from the Mozilla system as plugin viewport.
If its really an X Window you get, and not a widget from some specific toolkit (like GTK+ maybe?) then you can use the XGetWindowAttributes function call.
This fills out a provided XWindowAttributes structure, which includes integers for the x and y position of the window as well as its width and height and other useful facts.
But in reality I think you are probably using the Mozilla plugin API inherited from Netscape, aka NSAPI, and in that case what you get is a call to your function NPP_SetWindow() at least once (and again if necessary because something changed) with a structure which contains the information you're looking for. Try looking at http://www.mozilla.org/projects/plugins/ for more information about the APIs you should use.