eglfs: Avoid glUniform calls with wrong type when drawing the cursor

It is not really fatal but fixing it gets rid of a Mesa warning.

Change-Id: I3045b2691e7457541d6524c3e3ff8a1882ca460b
Reviewed-by: Gunnar Sletta <gunnar.sletta@digia.com>
Add assert if a global static is used after deletion.

Q_GLOBAL_STATIC accessor is documented to return dangling pointer if
called after destruction.

Change-Id: Ieafd5619b20ad256d9d5ad007d939f1430ef681f
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Olivier Goffart <ogoffart@woboq.com>
eglfs: Handle desktop and multiple windows gracefully

When trying to create more than one window, stop with a helpful error
message since this is not yet supported. Also, return a fake WId for
desktop windows.

Change-Id: I9859b62b1d4f6b6142982d2e5a90afc1fc3c6a28
Reviewed-by: Gunnar Sletta <gunnar.sletta@digia.com>
Remove redundant checks in some tools classes

This is a simple optimisation allowed to us by the fact that all platforms
we run on use two's complement for the signed integers. The trick works as
long as one of the two signed integers is known beforehand to be
non-negative:

 - by definition, for any signed integer i, i <= INT_MAX
 - by definition, for any unsigned integer u, u >= 0
 - given a signed integer x >= 0, 0U <= uint(x) <= uint(INT_MAX)
 - therefore, given another signed integer y of whatever
   value, uint(x) < uint(y) ←→ x < y && y >= 0

The trick is an optimisation because the compiler doesn't know that one of
the two sides is always non-negative. Otherwise, it would do the
same optimisation.

Change-Id: If256ec0df4e06335805af8010bb67ce5fd3e065a
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
eglfs: Set swap interval only when there is a context available

Mesa does not like eglSwapInterval calls without a current context.

Change-Id: I7ec2d4311586cf74da0461bc951a0e5d9399c35b
Reviewed-by: Gunnar Sletta <gunnar.sletta@digia.com>
Push updates to the QPA cursor even when a modal window is shown

Call QPlatformCursor::pointerEvent() even when the mouse event is
stopped due to being blocked by a modal window. This is necessary for
relatively dumb platforms, like eglfs, because the mouse cursor is
expected to be functional across the entire screen regardless of
having a modal dialog shown.

Platforms where the cursor is handled by the system (xcb, windows,
etc.) are not affected as they don't implement pointerEvent() anyway.

Change-Id: I4996ca0db23eb7f6ca3e2432d8d7abb1a5113dca
Reviewed-by: Gunnar Sletta <gunnar.sletta@digia.com>