Implement wp_viewporter support and fix scaling for fractional values

* 12to11.c (XLMain): Initialize wp_viewporter.
* Imakefile (ETAGS): Remove unused variable.
(SRCS, OBJS): Add wp_viewporter.c and wp_viewporter.o.
(GENHEADERS): Remove unnecessary headers.
(viewporter): New scanner target.
* README: Document support for wp_viewporter.
* compositor.h (struct _ViewportExt): New forward declaration.
(struct _DrawParams): New fields for cropping and stretching.
(struct _RenderFuncs): Describe how composite works.
(struct _BufferFuncs): Make update_buffer_for_damage take
DrawParams as an argument.
(struct _State): New fields for viewporting.
(struct _Surface): New field `viewport' and associated input
delta.
(struct _XdgRoleImplementationFuncs): New field
`is_window_mapped'.  Do not commit while unmapped.
* dmabuf.c (XLInitDmabuf): Remove outdated comment.
* dnd.c (HandleMotion): Use TruncateWindowToSurface.
* egl.c (struct _EglBuffer): Add 3x3 reverse transformation
matrix.
(struct _CompositeProgram): Rename `scale' to `source'.
(Index): New macro.
(PickBetterVisual, FindVisual): Compensate for EGL picking a
non-RGBA visual.
(EglCompileCompositeProgram): Look for source, not scale.
(ComputeTransformMatrix): New function.
(Composite): Compute transformation matrix and draw using that.
(BufferFromDmaBuf, BufferFromShm): Copy identity transform and
stop setting scale.
(ReverseTransformToBox): New function.
(UpdateShmBufferIncrementally): Accept DrawParams and invert
damage according to that.
(UpdateBuffer, UpdateBufferForDamage): Pass draw params to the
incremental buffer update function.
* fns.c (XLExtendRegion): New function.
* frame_clock.c (CurrentHighPrecisionTimestamp): Delete
function.
(HighPrecisionTimestamp, HighPrecisionTimestamp32): New
functions.
(PostEndFrame): Handle X server time truncation to 32 bits.
(XLFrameClockFreeze): Remove trailing whitespace.
* picture_renderer.c (GetSourceX, GetSourceY, CompareStretch):
New functions.
(MaybeApplyTransform): Check more values before applying
transformations.  Then, handle stretch and offset.
* positioner.c (GetAdjustmentOffset, ApplyConstraintAdjustment)
(XLPositionerCalculateGeometry): Scale coordinates using new
functions.
* renderer.c (RenderUpdateBufferForDamage): Accept DrawParams
instead of scale.
* shaders.txt (Composite Rectangle Fragment Shader RGBA)
(Composite Rectangle Fragment Shader RGBX)
(Composite Rectangle Fragment Shader External): Stop
transforming texcoords.
(Composite Rectangle Vertex Shader): Transform texcoords in the
vertex shader instead.
* subcompositor.c (IsViewported, SetViewported,
ClearViewported): New functions.
(struct _View): New fields for tracking viewports and fractional
offsets.
(ViewAttachBuffer): Do not garbage upon buffer size change if a
viewport is set.
(ViewMoveFractional): New function.
(ViewDamage): Describe what the damage is and is not transformed
by.
(GetContentScale): New function.
(ViewWidth, ViewHeight): Apply viewport.
(ViewSetScale): Use ViewAfterSizeUpdate instead of duplicating
code.
(ViewSetViewport, ViewClearViewport): New functions.
(ViewComputeTransform): Compute transform for viewports.  New
arg draw; use it to determine whether or not to include a
fractional offset.
(IntersectBoxes): Fix intersection calculation.
(SubcompositorUpdate): Don't keep calling ViewWidth and
ViewHeight in a loop.
(SubcompositorExpose): Adjust for changes to buffer damage
uploading.
* subsurface.c (MoveFractional): New function.  Handle
fractional offsets after scaling.
(MaybeUpdateOutputs, AfterParentCommit, Setup, Rescale): Use
that function to move the subsurface instead.
* surface.c (ApplyScale): Update comment.
(ApplyViewport, CheckViewportValues): New functions.
(HandleScaleChanged): Apply the viewport as well upon scale
change.
(ApplyDamage): Improve damage calculation for viewported
surfaces.
(SavePendingState, InternalCommit): Save and commit viewport
state; check old values upon buffer commit.
(InitState): Initialize viewport to initial values.
(XLSurfaceRunFrameCallbacks): Handle overflows of 32-bit time at
the 49-day mark.
(SurfaceToWindow, ScaleToWindow, WindowToSurface, ScaleToSurface)
(TruncateScaleToWindow, TruncateScaleToWindow)
(TruncateWindowToSurface, TruncateScaleToSurface): New functions
for handling scale.
* xdg_popup.c (MoveWindow, IsWindowMapped, XLGetXdgPopup):
* xdg_surface.c (IsRoleMapped, Commit, Subframe)
(GetResizeDimensions, XLXdgRoleCalcNewWindowSize):
* xdg_toplevel.c (IsWindowMapped, NoteConfigureTime, SendStates)
(RecordStateSize, HandleWindowGeometryChange, NoteWindowPreResize)
(XLGetXdgToplevel): Use them instead of manually multiplying
with the factor.

Imakefile

@@ -8,8 +8,6 @@ SYS_LIBRARIES = MathLibrary ThreadsLibraries
 DEPLIBS = $(DEPXLIB) $(DEPEXTENSIONLIB) $(DEPXRANDRLIB) $(DEPXRENDERLIB) \
   $(DEPXFIXESLIB) $(DEPXILIB) $(DEPXKBFILELIB)
 
-ETAGS = etags
-
 LOCAL_LIBRARIES = $(XLIB) $(EXTENSIONLIB) $(XCBLIB) $(XCB) $(XCB_SHM)      \
   $(XRANDRLIB) $(PIXMAN) $(XRENDERLIB) $(XILIB) $(XKBFILELIB) $(XFIXESLIB) \
   $(XCB_DRI3) $(XCB_SHAPE) $(WAYLAND_SERVER)
@@ -22,7 +20,8 @@ SRCS = 12to11.c run.c alloc.c fns.c output.c compositor.c       \
   ewmh.c timer.c subsurface.c seat.c data_device.c xdg_popup.c  \
   dmabuf.c buffer.c select.c xdata.c xsettings.c dnd.c          \
   icon_surface.c primary_selection.c renderer.c                 \
-  picture_renderer.c explicit_synchronization.c
+  picture_renderer.c explicit_synchronization.c transform.c     \
+  wp_viewporter.c
 
 OBJS = 12to11.o run.o alloc.o fns.o output.o compositor.o       \
   surface.o region.o shm.o atoms.o subcompositor.o positioner.o \
@@ -30,11 +29,10 @@ OBJS = 12to11.o run.o alloc.o fns.o output.o compositor.o       \
   ewmh.o timer.o subsurface.o seat.o data_device.o xdg_popup.o  \
   dmabuf.o buffer.o select.o xdata.o xsettings.o dnd.o          \
   icon_surface.o primary_selection.o renderer.o                 \
-  picture_renderer.o explicit_synchronization.o
+  picture_renderer.o explicit_synchronization.o transform.o     \
+  wp_viewporter.o
 
-GENHEADERS = transfer_atoms.h primary-selection-unstable-v1.h \
-  linux-dmabuf-unstable-v1.h xdg-shell.h                      \
-  linux-explicit-synchronization-unstable-v1.h
+GENHEADERS = transfer_atoms.h
 
 #ifdef HaveEglSupport
 
@@ -111,6 +109,7 @@ ScannerTarget(linux-dmabuf-unstable-v1)
 ScannerTarget(xdg-shell)
 ScannerTarget(primary-selection-unstable-v1)
 ScannerTarget(linux-explicit-synchronization-unstable-v1)
+ScannerTarget(viewporter)
 
 /* Make OBJS depend on scanner headers, and depend on both them and SRCS.  */
 $(OBJS): $(GENHEADERS)