When rendering text, especially truetype fonts, we would use the next
character avance metric to check if the character fits in the target
surface. This commit changes it to use the bounding box metric. The
bounding box represents the actual pixels that will be touched when
drawing the character.
This fixes an issue noticed on the main menu of Myst ME where the last
character of the string "OPTIONEN" would not be rendered despite there
being enough room to render it. More precisely, this ensures that
calling Font::getBoundingBox for a string, and then passing a surface
exactly the size of the returned bounding box to the draw function
actually renders all the characters.
Since Graphics::loadThumbnail can return successfully when a thumbnail is skipped
the caller may want to check to the see that the thumbnail is not null before using
it. Setting it to null is just defensive in case the caller didn't do so.
If the user tries to use the thumbnail in setThumbnail then it will just
show a black screen for the thumbnail rather than crashing if they have
not set the thumbnail to null.
This commit introduces the following changes:
1. Graphics::loadThumbnail()
Now returns a boolean and takes a new argument skipThumbnail which
defaults to false. In case of true, loadThumbnail() reads past the
thumbnail data in the input stream instead of actually loading the
thumbnail. This simplifies savegame handling where, up until now,
many engines always read the whole savegame metadata (including
the thumbnail) and then threw away the thumbnail when not needed
(which is in almost all cases, the most common exception being
MetaEngine::querySaveMetaInfos() which is responsible for loading
savegame metadata for displaying it in the GUI launcher.
2. readSavegameHeader()
Engines which already implement such a method (name varies) now take
a new argument skipThumbnail (default: true) which is passed
through to loadThumbnail(). This means that the default case for
readSavegameHeader() is now _not_ loading the thumbnail from a
savegame and just reading past it. In those cases, e.g.
querySaveMetaInfos(), where we actually are interested in loading
the thumbnail readSavegameHeader() needs to explicitely be called
with skipThumbnail == false.
Engines whose readSavegameHeader() (name varies) already takes an
argument loadThumbnail have been adapted to have a similar
prototype and semantics.
I.e. readSaveHeader(in, loadThumbnail, header) now is
readSaveHeader(in, header, skipThumbnail).
3. Error handling
Engines which previously did not check the return value of
readSavegameHeader() (name varies) now do so ensuring that possibly
broken savegames (be it a broken thumbnail or something else) don't
make it into the GUI launcher list in the first place.
Drawing nows happens directly when the Dialog or Widget draw methods are
called. This makes it easy to debug why a particular low level draw
method was called, by inspecting the call stack.
This replaces the notion of "buffering" by two independant ways to
control what is drawn and where:
- The active layer is used to select whether the foreground or
background part of the dialogs are rendered by the draw calls.
- The active surface is used to select if the draw calls affect the back
buffer or the screen.
The foreground layer of the active dialog is drawn directly to the
screen. Its background layer is drawn to the back buffer. This way
widgets can restore the back buffer in order to update without having to
redraw the dialog's background.
Dialogs lower in the dialog stack are drawn entirely to the back buffer.
When drawing a rounded rectangle, first its shadow is drawn, and then
the rectangle proper is drawn over it. This optimization skips drawing
a shadow rectangle that is entirely occluded by the main rectangle.
A quick benchmark shows large improvements to the modern theme GUI draw
speed. On a 1 GHz ARMv7 CPU with optimizations enabled, drawing the add
game dialog @ 1920x1080 went from 976 ms to 136 ms.
