This patch adds itemAtIndex method to ItemView-derived views and
to PathView.

[ChangeLog][QtQuick][QQuickItemView] Added itemAtIndex() to
GridView, ListView and PathView to fetch a visible delegate by index.

Change-Id: Id8475d06c1481036984fe5109bb52cf2729b1c21
Fixes: QTBUG-72961
Reviewed-by: Shawn Rutledge <shawn.rutledge@qt.io>

The margin has to be taken into account when calculating the positions
for the dimension we are not scrolling and when calculating the number
of columns available.

Fixes: QTBUG-69863
Change-Id: Id2a53ced263c8926a8bfaf658376be293af3e8c9
Reviewed-by: Richard Moe Gustavsen <richard.gustavsen@qt.io>

VisualDataModel, VisualDataGroup, and VisualItemModel
are replaced with DelegateModel, DelegateModelGroup, and
ObjectModel respectively (since
7cad0e52c5a020bd29635e9912fd8946a6b48124).

Also renamed/deleted a few snippet files and an image.

Task-number: QTBUG-37725
Change-Id: I5fa93993a31d8f9b08e7a282d5550ddd9bfb813f
Reviewed-by: Shawn Rutledge <shawn.rutledge@qt.io>

The changes made in 134d980a7fcf61c5440019bcfb3fdfc39c3f5f3c and
2b779fbd25aaf09897ee2cdc4edffd12a980420b were still a bit too broad.
Tighten the condition further so original behavior is restored
for smaller to medium drags.

Change-Id: I9006e9cea80c1ef79e0b8d6a47b2a497532bef57
Reviewed-by: Mitch Curtis <mitch.curtis@qt.io>

Previously small and large flicks would go to the next item, but there
was a small range just under halfway where it would snap to the previous
position (most easily hit with smaller delegates). Get rid of this
blindspot.

Change-Id: Ib8d026cad9427b2d209a9646b3ea515f578457ae
Reviewed-by: Mitch Curtis <mitch.curtis@qt.io>

Task-number: QTBUG-68933
Change-Id: Ibb5aa227e82825085e7214e17dcffcb17fd44157
Reviewed-by: Topi Reiniö <topi.reinio@qt.io>

From now on we prefer nullptr instead of 0 to clarify cases where
we are assigning or testing a pointer rather than a numeric zero.

Also, replaced cases where 0 was passed as Qt::KeyboardModifiers
with Qt::NoModifier (clang-tidy replaced them with nullptr, which
waas wrong, so it was just as well to make the tests more readable
rather than to revert those lines).

Change-Id: I4735d35e4d9f42db5216862ce091429eadc6e65d
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>

 Conflicts:
	src/plugins/qmltooling/qmldbg_profiler/qqmlprofilerservice.cpp
	src/qml/compiler/qqmlirbuilder.cpp
	src/qml/compiler/qqmlirbuilder_p.h
	src/qml/compiler/qqmltypecompiler.cpp
	src/qml/compiler/qv4codegen.cpp
	src/qml/compiler/qv4codegen_p.h
	src/qml/compiler/qv4compileddata_p.h
	src/qml/compiler/qv4compiler.cpp
	src/qml/compiler/qv4compilercontext_p.h
	src/qml/compiler/qv4isel_moth.cpp
	src/qml/compiler/qv4jsir.cpp
	src/qml/compiler/qv4jsir_p.h
	src/qml/jit/qv4isel_masm.cpp
	src/qml/jsruntime/qv4engine.cpp
	src/qml/jsruntime/qv4functionobject.cpp
        src/qml/jsruntime/qv4runtimecodegen.cpp
	src/qml/jsruntime/qv4script.cpp
	src/qml/jsruntime/qv4script_p.h
	src/qml/qml/qqmltypeloader.cpp
	src/quick/items/qquickanimatedimage.cpp
	src/quick/items/qquickanimatedimage_p_p.h
	src/quick/scenegraph/compressedtexture/qsgpkmhandler.cpp
	tests/auto/qml/qmlplugindump/qmlplugindump.pro
	tests/auto/qml/qmlplugindump/tst_qmlplugindump.cpp
	tools/qmlcachegen/qmlcachegen.cpp
	tools/qmljs/qmljs.cpp

Done-with: Shawn Rutledge <shawn.rutledge@qt.io>
Done-with: Lars Knoll <lars.knoll@qt.io>
Done-with: Ulf Hermann <ulf.hermann@qt.io>
Change-Id: I010e6525440a85f3b9a10bb9083f8e4352751b1d

The block for finding the position for the item *before* needs to be
applied for the case where visibleItems is empty too, so we separate it
out.

Change-Id: I60a7e3a44d01a0087970e37bf4e73b94da5ebd48
Task-number: QTBUG-49218
Reviewed-by: Shawn Rutledge <shawn.rutledge@qt.io>

 Conflicts:
	.qmake.conf
	src/qml/memory/qv4mm.cpp
	src/qml/qml/qqmlbinding.cpp

Change-Id: I98e51ef5af12691196da5772a07d3d53d213efcc