[Qgis-developer] Plans for QGIS 3.0 and QWebView.... *sigh*

[Matthias Kuhn]

QtWebKit is not removed, is it?

On 09/14/2016 08:17 AM, Nyall Dawson wrote:
> Sooooo... now that we're close to cutting off Qt4 I guess it's time to
> start this conversation again. What should we do with web views in
> QGIS 3.0?
> 
> Here's the situation as I see it:
> 
> - upstream still hasn't made the new QtWebEngine classes anywhere near
> as featureful as the removed QWebView classes. I was hoping by the
> time we were ready for Qt5 this would have changed, but there hasn't
> been any really relevant changes since we last discussed this.
> 
> - the one minor expection to this is a new method which was added in
> Qt 5.7 - QtWebEngine::printToPdf [1] . The docs say:
> 
> "Renders the current content of the page into a PDF document and saves
> it in the location specified in filePath. The page size and
> orientation of the produced PDF document are taken from the values
> specified in pageLayout."
> 
> Potentially we could use this as a roundabout way of rendering web
> content offscreen - we could print the content out to a pdf, then
> somehow read it back in and render it to a QPainter surface. Maybe. I
> haven't been able to test this, but I have extreme doubts. Just
> looking at the docs I can't see anyway to control the DPI used for
> printing the content to a pdf, and my suspicion is that it will just
> be rendered using screen resolution.
> 
> Even with the long shot that we could successfully use this method
> it's still only available in Qt 5.7, which won't hit our target
> platform repos until mid 2029 ;)
> 
> - Possibly we could use the revived QtWebKit (see [2]), but we'd
> probably need to package it ourselves. Advantages of this approach are
> numerous, including no loss of current features.
> 
> 
> Given all this... I think our realistic options are:
> 
> 1 Don't use a web engine. Use QTextDocument and it's limited html/css
> support. Disadvantages: we lose the ability to insert rich html
> including javascript, etc. Advantages: retain vector outputs and
> simple code.
> 
> 2 Render QtWebEngineView widgets as rasters in screen resolution.
> Disadvantages: pixelated, not vectorised and text converted to raster,
> requires use of a graphical widget which may cause issues with things
> like QGIS server (?). Advantages: can use javascript, videos, etc
> 
> 
> 
> My opinion:
> 
> QgsComposerLabel - approach 1. Switch to the basic QTextDocument support
> 
> HTML annotations - approach 2. These are likely used more often in the
> canvas interactively and the loss of resolution when they are used in
> composer is less important.
> 
> QgsComposerHTML - no idea. Probably option 2 but the loss of
> resolution/vector output will really hurt.
> 
> 
> It's probably time for us to address this, so we need to make a choice
> between these bad options. Any suggestions?
> 
> Nyall
> 
> 
> [1] http://doc.qt.io/qt-5/qwebenginepage.html#printToPdf
> [2] http://qtwebkit.blogspot.com.au/2016/08/qtwebkit-im-back.html
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