[Development] The behaviour of Image / image provider are different from 5.5.1 to 5.6 in iOS

[Ben Lau]

On 11 April 2016 at 19:59, ekke <ekke at ekkes-corner.org> wrote:

> Am 11.04.16 um 12:38 schrieb Ben Lau:
>
> Hi,
>
> I am writing an image provider that read all the images to memory at
> startup. And I found that the behaviour is different from 5.5.1 to 5.6 in
> iOS. Seems that it is undocumented. I wonder is it an expected behaviour or
> a bug?
>
> That is the example project:
> https://github.com/benlau/quickcross/tree/master/tests/imageprovider
>
> That is the code of my image provider:
>
> QImage QCImageProvider::requestImage(const QString &id, QSize *size, c
> onst QSize &requestedSize)
>
> {
>
>     Q_UNUSED(requestedSize);
>
>     QCImageLoader* loader = QCImageLoader::instance();
>
>     QImage result;
>
>     if (loader->contains(id)) {
>
>         result = loader->image(id);
>
>         *size = result.size();
>
>     }
>
>     return result;
>
> }
>
> Code to display image:
>
> Image {
>
>   id: image
>
>   source: "image://arts/Lenna.png" // An 512x512 image
>
> }
>
> In Qt 5.5.1 with iPhone6, the property of image will be set to:
>
> width: 512
>
> height: 512
>
> sourceSize: Qt.size(512,512)
>
> However, in Qt 5.6 with iPhone6, it becomes:
>
> width: 170.66666
>
> height: 170.66666
>
> sourceSize: Qt.size(512,512)
>
> The display size of image is different.
>
>
> now from Qt 5.6 HighDPI is supported for all platforms.
> iPhone has scaling factor 3
>
> 170.66666 * 3 = 512
>
>
> ekke
>
>
But Qt 5.5 on iOS also support HighDPI. Their result are different.
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