Qt embedded, touchscreens, and cursors

Qt embedded, touchscreens, and cursors

[Steve Sakoman]

I'm new to the Qt world, so perhaps this is a stupid question . . .

I'm helping a client create a custom layer for their touchscreen based
hardware and Qt applications.

They've decided to use Qt4e and we are including the stock danny qt4e
binaries in the image.

All works as desired with one exception:  the Qt cursor appears at app
launch time with a green 16x16 background, converts to the app
background shortly thereafter, and then stays on the screen until the
first time you touch the screen, then disappears and stays gone.

Some quick googling indicates this is a common problem with touchsceen
Qt implementations and that there are no satisfactory runtime
solutions.  The most often recommended solution is to disable the
cursor at build time with -no-feature-CURSOR added to the Qt config
options.  This option is also claimed to give a significant
performance boost.

I tried adding a bbappend to add this option, but as some of the above
mentioned sources indicated the Qt build will fail unless you disable
demos, examples, and a couple of other build features.  I started
going down this path but I suspect it will require changes to the base
Qte recipe.

Have others run into this issue?  I suspect that most target hardware
for Yocto builds are touchscreen based, so this will likely come up
over and over again.

Any suggestions?

Steve

Re: Qt embedded, touchscreens, and cursors

[Eric Bénard]

Hi Steve,

Le Tue, 25 Jun 2013 09:34:05 -0700,
Steve Sakoman <sakoman@gmail.com> a écrit :

> I'm new to the Qt world, so perhaps this is a stupid question . . .
> 
> I'm helping a client create a custom layer for their touchscreen based
> hardware and Qt applications.
> 
> They've decided to use Qt4e and we are including the stock danny qt4e
> binaries in the image.
> 
> All works as desired with one exception:  the Qt cursor appears at app
> launch time with a green 16x16 background, converts to the app
> background shortly thereafter, and then stays on the screen until the
> first time you touch the screen, then disappears and stays gone.
> 
> Some quick googling indicates this is a common problem with touchsceen
> Qt implementations and that there are no satisfactory runtime
> solutions.  The most often recommended solution is to disable the
> cursor at build time with -no-feature-CURSOR added to the Qt config
> options.  This option is also claimed to give a significant
> performance boost.
> 
> I tried adding a bbappend to add this option, but as some of the above
> mentioned sources indicated the Qt build will fail unless you disable
> demos, examples, and a couple of other build features.  I started
> going down this path but I suspect it will require changes to the base
> Qte recipe.
> 
> Have others run into this issue?  I suspect that most target hardware
> for Yocto builds are touchscreen based, so this will likely come up
> over and over again.
> 
> Any suggestions?

IIRC you can hack this in 
qwscursor_qws.cpp
around "// default cursor"
you change ArrowCursor to BlankCursor
(sorry no clean patch for that ATM).

Eric

Re: Qt embedded, touchscreens, and cursors

[Steve Sakoman]

On Thu, Jun 27, 2013 at 1:03 AM, Eric Bénard <eric@eukrea.com> wrote:

> IIRC you can hack this in
> qwscursor_qws.cpp
> around "// default cursor"
> you change ArrowCursor to BlankCursor
> (sorry no clean patch for that ATM).

Hi Eric,

That is exactly what I ended up doing.  The -no-feature-CURSOR
approach caused too many issues, i.e. breakage in demos, samples, and
tools.

For the record, here is the patch I used:

diff --git a/src/gui/embedded/qwscursor_qws.cpp
b/src/gui/embedded/qwscursor_qws.cpp
index 9e8c235..0ff0dc3 100644
--- a/src/gui/embedded/qwscursor_qws.cpp
+++ b/src/gui/embedded/qwscursor_qws.cpp
@@ -344,7 +344,7 @@ void QWSServerPrivate::initializeCursor()

     // default cursor
     cursor = 0;
-    setCursor(QWSCursor::systemCursor(Qt::ArrowCursor));
+    setCursor(QWSCursor::systemCursor(Qt::BlankCursor));
 #endif
     q->sendMouseEvent(QPoint(swidth/2, sheight/2), 0);
 }