[QScintilla] Scrolling content of QScintilla viewport

[Phil Thompson]

On 18/07/2015 12:54 am, fulcrumusa at aim.com wrote:
>> You could try the low level SCI_LINESCROLL...
>> 
>> 
> http://www.scintilla.org/ScintillaDoc.html#SCI_LINESCROLL
> 
> 
> Hi Phil,
> 
> Thank you
> for the suggestion. I did try that (after digging through the
> QScintilla code because SF.net is down :)).

The Scintilla docs are in the source package.

> While I can scroll the text, I am getting somewhat
> inconsistent behavior from QScintilla editor even without scrolling.
> 
> I have the following code now:
> 
>         self.file = QFile(filename)
>         if not self.file.open(QIODevice.ReadOnly):
>             print "Error opening file", filename
> 
>         self.editor.read(self.file)
>         size = self.editor.viewport().frameSize()
>         font = self.lexer.defaultFont(0)
> 
>         fontmetrics = QFontMetrics(font)
>         print "viewport size %u, line spacing: %u" % \
>               (size.height(), fontmetrics.lineSpacing())
> 
>         num_lines = size.height() / fontmetrics.lineSpacing()
>         print "number of lines on screen %d" % num_lines
>         scroll_by_lines = (num_lines / 2)
> 
>         self.editor.setFocus()
> 
>         self.editor.SendScintilla(Qsci.QsciScintilla.SCI_GOTOLINE, 
> line)
> 
>         #self.editor.setSelection(line - 1, 0, line, 0)
>         #self.editor.setSelectionBackgroundColor(QColor("#cccccc"))
>         self.editor.recolor()
>         print "scrolling by %d lines" % scroll_by_lines
>         #self.editor.SendScintilla(Qsci.QsciScintilla.SCI_LINESCROLL, 
> 0,
>         #                                   scroll_by_lines)
> 
> As you can see, I use the raw SCI_GOTOLINE command to put the
> editor at the desired line. However, the line is not always visible as 
> the
> documentation says it should be. If the viewport is small, the line is 
> just
> below the visible area.
> If it is large, the target line is always 6 lines from the bottom of
> the viewable
> area.
> 
> Furthermore, regardless of how big I resize the editor widget to,
> self.editor.viewport().frameSize() always returns the same size.
> 
> How does QScintilla determine the size of the viawable are?

It's all related to the manipulation of the scrollbars. See the 
scrollbar related functions in ScintillaQt.cpp.

Phil