Since there are no mutable borrows in the WindowDrawList API, we can remove all
draw functions from ChannelsSplit and just use the same `draw_list' all
the time, as shown in the `WindowDrawList::channels_split` example.
This approach makes the `DrawAPI` trait pointless so it can be removed, and
ChannelsSplit is reduced to a type with just one function:
`set_current`.
At run time, the environment checks that at most one instance of
WindowDrawList exists using a static boolean: WINDOW_DRAW_LIST_LOADED.
If two WindowDrawList could exist at the same time, there would be
several instances of the same `*mut ImDrawList`, which could lead
to unfathomable bad things.
When a WindowDrawList is created, WINDOW_DRAW_LIST_LOADED is set to
true. And when it is dropped, WINDOW_DRAW_LIST_LOADED is set to false.
Creating a new WindowDrawList while WINDOW_DRAW_LIST_LOADED is true
causes a panic.
AtomicBool could have been used instead of a bool for
WINDOW_DRAW_LIST_LOADED. Though it allows to avoid the use of `unsafe { }`,
the construct we are doing is already inherently unsafe.
WindowDrawList and Ui are !Send and !Sync, so they cannot anyway be shared
among threads.
So we'd better be explicit and use an unsafe block with a normal bool.
The test was failing because no `main` function was defined, as explained
in the rustdoc documentation [1].
Add the "no_run" flag. This way, there is no attempt to run the test
code. Only compile checks are done. Thus defining a `main` function is
unnecessary.
Moreover "export crate imgui" is implicit, so removed.
[1] https://doc.rust-lang.org/stable/rustdoc/documentation-tests.html#pre-processing-examples.
This commit adds two methods to the drawing APIs: with_clip_rect and
with_clip_rect_intersect.
Both wrap ImDrawList_PushClipRect and ImDrawList_PopClipRect.
However, with_clip_rect_intersect sets the `intersect` argument of
ImDrawList_PushClipRect to `true`.
As `add_rect_filled_multicolor` does not have any option, the `build`
pattern is not used and calling `add_rect_filled_multicolor` directly
draws the rectangle on the window.
This patch uses bitflags to set the whether the corners are rounded.
Hence the `ImDrawCornerFlags` struct is defined, but only used
internally.
Externally, the valule of the flags can be changed with methods on the
`Rect` structure such as `round_top_right` or `round_bot_left`.
This patch wraps both ImDrawList_AddRectFilled and ImDrawList_AddRect.
ImDrawList_AddRectFilled is seen as a particular case of `add_rect`
where `filled` is set to `true`.
This patch makes the basic structure for a wrapper around Dear ImGui's
drawing API.
1. Implement `with_window_draw_list` method on Ui. Call this method to
get access to the `WindowDrawList` object. This object holds the methods
to access ImGui's drawing API.
2. Dear ImGui uses the ImU32 (an unsigned c_int) to represent colors in
the drawing API. This commit wraps this type with ImColor for
convenience. Any color representation (3or4-tuples, 3or4-arrays, ImU32
or ImVec4) can be converted into ImColor for convenience.
3. Difference between WindowDrawList and ChannelsSplit: Most drawing
functions can be called on WindowDrawList and ChannelsSplit objects.
However for safety, some functions can only be called on WindowDrawList
or ChannelsSplit instance. For example `channels_set_current` can only
be called after channels have been split. To avoid code duplication,
functions common to WindowDrawList and ChannelsSplit are implemented
within the `impl_draw_list_methods` macro.
4. Implement drawing functions (in this commit, add_line only). Calling
`add_line` returns a default representation of the line to be drawn, but
does not draw it. Then parameters, such as thickness, can be set. You
must call `build` to draw the line. All drawing functions will be
implemented following this pattern.
