[Interest] animation on font.pixelSize

[Thomas Senyk]

On Fri, January 11, 2013 10:21:11 Jason H wrote:
> Try scale, not pixelSize.
> http://blog.qt.digia.com/blog/2011/07/15/text-rendering-in-the-qml-scene-gra
> ph/ "scalable, sub-pixel positioned and sub-pixel antialiased… and at almost
> no cost."
> 

Sure, I can use scale.
Problem is, scale doesn't behave as nicely as pixelSize in terms of position 
and size (x,y, anchors,...)

>From an feature/behavior point of view their isn't much to gain from having 
different implementations for pixel-size and scale 
... both end up with a glyph being painted with a specific GLsize to a 
specific position using the same glyph-texture-atlas
 ... or not? :)


I'm just trying to understand :)

Greets
Thomas
 

 

> 
> 
> ________________________________
>  From: Thomas Senyk <thomas.senyk at pelagicore.com>
> To: interest at qt-project.org
> Sent: Friday, January 11, 2013 10:59 AM
> Subject: [Interest] animation on font.pixelSize
> 
> Hi,
> 
> as with Quick2.0 we got the very nice DistanceField-font-rendering.
> So in theory animations on Text{ font.pixelSize } should be fairly cheap,
> right?
> 
> With the following code snipped I got performance problems never the less:
> 
> import QtQuick 2.0
> Text {
>     id: text
>     width: 500
>     height: 100
>     text: "Test font.pixelSize animation"
>     NumberAnimation {
>         running: true
>         loops: Animation.Infinite
>         duration: 2000
>         target: text
>         property: "font.pixelSize"
>         from: 10
>         to: 90
>     }
> }
> 
> 
> The strange thing is, on my desktop he has 100% cpu load for the first 2-4
> loops.
> ... I wild guess: It looks like it needs to render the font-glyphs for
> each(?) size and after a few cycles it got all of them rendered and
> cached...? (it can't render all of them in the first loop as he jumps due
> to bad performance)
> 
> On embedded (raspberry pi) I get <20% load all the time.
> 
> On desktop I got:
> - intel xeon 3ghz
> - nvidia 8600gts
> - Qt5 checkout from this week, branch: stable
> - xcb as platform backend (using freetype and fontconfig)
> 
> On the raspberry  I got:
>   - BCM 2835 (slow ARM11 cpu, fast VideoCore IV GPU)
>   - eglfs as platform backend
>   - no fontconfig -> QBasicFontDatabase
> (If it helps I can do a fontconfig build)
> 
> Is this know? Can anyone verify?
> And possible explanation? .. maybe my Qt5 build on desktop is flawed?
> 
> 
> (If this belongs to development at qt-project.org, feel free to move)
> 
> Greets
> Thomas
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