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WindowServer: Support windows with alpha channels. And per-WSWindow opacity.

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This patch also adds a Format concept to GraphicsBitmap. For now there are
only two formats: RGB32 and RGBA32. Windows with alpha channel have their
backing stores created in the RGBA32 format.

Use this to make Terminal windows semi-transparent for that comfy rice look.
There is one problem here, in that window compositing overdraw incurs
multiple passes of blending of the same pixels. This leads to a mismatch in
opacity which is obviously not good. I will work on this in a later patch.

The alpha blending is currently straight C++. It should be relatively easy
to optimize this using SSE instructions.

For now I'm just happy with the cute effect. :^)
This commit is contained in:
Andreas Kling 2019-02-19 01:42:53 +01:00
parent d4973842c9
commit 9b71307d49
25 changed files with 244 additions and 71 deletions
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53
SharedGraphics/Painter.cpp
View file

@ -32,7 +32,10 @@ Painter::Painter(GWidget& widget)
request.window_id = widget.window()->window_id();
auto response = GEventLoop::main().sync_request(request, WSAPI_ServerMessage::DidGetWindowBackingStore);
m_target = GraphicsBitmap::create_with_shared_buffer(response.backing.shared_buffer_id, response.backing.size);
m_target = GraphicsBitmap::create_with_shared_buffer(
response.backing.has_alpha_channel ? GraphicsBitmap::Format::RGBA32 : GraphicsBitmap::Format::RGB32,
response.backing.shared_buffer_id,
response.backing.size);
ASSERT(m_target);
m_window = widget.window();
m_translation.move_by(widget.window_relative_rect().location());
@ -67,7 +70,7 @@ void Painter::fill_rect_with_draw_op(const Rect& a_rect, Color color)
for (int i = rect.height() - 1; i >= 0; --i) {
for (int j = 0; j < rect.width(); ++j)
set_pixel_with_draw_op(dst[j], color.value());
set_pixel_with_draw_op(dst[j], color);
dst += dst_skip;
}
}
@ -230,8 +233,17 @@ void Painter::draw_bitmap(const Point& p, const GlyphBitmap& bitmap, Color color
}
}
void Painter::blit_with_alpha(const Point& position, const GraphicsBitmap& source, const Rect& src_rect)
void Painter::blit_with_opacity(const Point& position, const GraphicsBitmap& source, const Rect& src_rect, float opacity)
{
ASSERT(!m_target->has_alpha_channel());
if (!opacity)
return;
if (opacity >= 1.0f)
return blit(position, source, src_rect);
byte alpha = 255 * opacity;
Rect dst_rect(position, src_rect.size());
dst_rect.move_by(m_translation);
auto clipped_rect = Rect::intersection(dst_rect, m_clip_rect);
@ -248,13 +260,42 @@ void Painter::blit_with_alpha(const Point& position, const GraphicsBitmap& sourc
for (int row = first_row; row <= last_row; ++row) {
for (int x = 0; x <= (last_column - first_column); ++x) {
byte alpha = Color(src[x]).alpha();
Color src_color_with_alpha = Color::from_rgb(src[x]);
src_color_with_alpha.set_alpha(alpha);
Color dst_color = Color::from_rgb(dst[x]);
dst[x] = dst_color.blend(src_color_with_alpha).value();
}
dst += dst_skip;
src += src_skip;
}
}
void Painter::blit_with_alpha(const Point& position, const GraphicsBitmap& source, const Rect& src_rect)
{
ASSERT(source.has_alpha_channel());
Rect dst_rect(position, src_rect.size());
dst_rect.move_by(m_translation);
auto clipped_rect = Rect::intersection(dst_rect, m_clip_rect);
if (clipped_rect.is_empty())
return;
const int first_row = clipped_rect.top() - dst_rect.top();
const int last_row = clipped_rect.bottom() - dst_rect.top();
const int first_column = clipped_rect.left() - dst_rect.left();
const int last_column = clipped_rect.right() - dst_rect.left();
RGBA32* dst = m_target->scanline(clipped_rect.y()) + clipped_rect.x();
const RGBA32* src = source.scanline(src_rect.top() + first_row) + src_rect.left() + first_column;
const size_t dst_skip = m_target->width();
const unsigned src_skip = source.width();
for (int row = first_row; row <= last_row; ++row) {
for (int x = 0; x <= (last_column - first_column); ++x) {
byte alpha = Color::from_rgba(src[x]).alpha();
if (alpha == 0xff)
dst[x] = src[x];
else if (!alpha)
continue;
else
dst[x] = Color(dst[x]).blend(src[x]).value();
dst[x] = Color::from_rgba(dst[x]).blend(Color::from_rgba(src[x])).value();
}
dst += dst_skip;
src += src_skip;
@ -263,6 +304,8 @@ void Painter::blit_with_alpha(const Point& position, const GraphicsBitmap& sourc
void Painter::blit(const Point& position, const GraphicsBitmap& source, const Rect& src_rect)
{
if (source.has_alpha_channel())
return blit_with_alpha(position, source, src_rect);
Rect dst_rect(position, src_rect.size());
dst_rect.move_by(m_translation);
auto clipped_rect = Rect::intersection(dst_rect, m_clip_rect);