* imgui: Clamp mouse y-coordinate in multi-line click/drag to text bounds
In single-line mode, click and drag already clamped y to the line's
y-coordinate so the cursor would continue to follow the x-position when
the mouse went off the top or bottom of the text. Multi-line mode did
not clamp, so stb_text_locate_coord() would return 0 (above) or n
(below), snapping the cursor to the very start or end of text and
ignoring the x-coordinate entirely.
Now both modes walk the row layout to compute the top of the first row
(y_min) and bottom of the last row (y_max, minus half a line height to
add tolerance for rounding), then clamp y to that range before passing
it to stb_text_locate_coord(). This means dragging or clicking above
the text now places the cursor on the first line at the x-coordinate,
and dragging/clicking below places it on the last line at the
x-coordinate, matching the single-line precedent.
* Fix issue that cursor cannot be placed at the last empty line
Move many third-party components' source codes from the src folder to a new folder called deps_src. The goal is to make the code structure clearer and easier to navigate.
