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docs(background_manager): add comments

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Benno Fünfstück 2018-08-13 18:38:36 +02:00 committed by Patrick Ziegler
parent 4221da71bf
commit 15b84dda07
1 changed files with 41 additions and 1 deletions
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42
include/x11/background_manager.hpp
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@ -16,6 +16,13 @@ namespace cairo {
class xcb_surface;
}
/**
* \brief Class to keep track of the desktop background used to support pseudo-transparency
*
* For pseudo-transparency that bar needs access to the desktop background.
* We only need to store the slice of the background image which is covered by the bar window,
* so this class takes a rectangle that limits what part of the background is stored.
*/
class background_manager : public signal_receiver<SIGN_PRIORITY_SCREEN, signals::ui::update_geometry>,
public xpp::event::sink<evt::property_notify>
{
@ -23,29 +30,62 @@ class background_manager : public signal_receiver<SIGN_PRIORITY_SCREEN, signals:
using make_type = background_manager&;
static make_type make();
/**
* Initializes a new background_manager that by default does not observe anything.
*
* To observe a slice of the background you need to call background_manager::activate.
*/
explicit background_manager(connection& conn, signal_emitter& sig, const logger& log);
~background_manager();
/**
* Starts observing a rectangular slice of the desktop background.
*
* After calling this function, you can obtain the current slice of the desktop background
* with background_manager::get_surface. Whenever the background slice changes (for example,
* due to bar position changes or because the user changed the desktop background) the class
* emits a signals::ui::update_background event.
*
* \param window This should be set to the bar window.
* \param rect Slice of the background to observe (coordinates relative to window).
* Typically set to the outer area of the bar.
*/
void activate(xcb_window_t window, xcb_rectangle_t rect);
/**
* Stops observing the desktop background and frees all resources.
*/
void deactivate();
/**
* Retrieve the current desktop background slice.
*
* This function returns a slice of the desktop background that has the size of the rectangle
* given to background_manager::activate. As the slice is cached by the manager, this function
* is fast.
*/
cairo::surface* get_surface() const;
void handle(const evt::property_notify& evt);
bool on(const signals::ui::update_geometry&);
private:
// references to standard components
connection& m_connection;
signal_emitter& m_sig;
const logger& m_log;
xcb_window_t m_window;
// these are set by activate
xcb_window_t m_window;
xcb_rectangle_t m_rect{0, 0, 0U, 0U};
// required values for fetching the root window's background
xcb_visualtype_t* m_visual{nullptr};
xcb_gcontext_t m_gcontext{XCB_NONE};
xcb_pixmap_t m_pixmap{XCB_NONE};
unique_ptr<cairo::xcb_surface> m_surface;
// true if we are currently attached as a listener for desktop background changes
bool m_attached{false};
void allocate_resources();