7b75d0a256
By default, wxMSW overlay uses a constant alpha for the window's opacity which can be changed by the added wxOverlay::SetOpacity() function. For some applications, that's all they need. But for others, per-pixel alpha blending is a requirement. This capability can be enabled by calling SetOpacity(-1) before initializing the overlay. But the drawing must be done via a graphics context because the standard DC under MSW does not support alpha drawing. Also request that the overlay window be positioned below any floating windows on the target (if any).
86 lines
2.3 KiB
Objective-C
86 lines
2.3 KiB
Objective-C
/////////////////////////////////////////////////////////////////////////////
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// Name: overlay.h
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// Purpose: interface of wxOverlay
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// Author: wxWidgets team
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// Licence: wxWindows licence
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/////////////////////////////////////////////////////////////////////////////
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/**
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@class wxOverlay
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Creates an overlay over an existing window, allowing for manipulations like
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rubberbanding, etc. On wxOSX the overlay is implemented with native
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platform APIs, on the other platforms it is simulated using wxMemoryDC.
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@library{wxcore}
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@see wxDCOverlay, wxDC
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*/
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class wxOverlay
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{
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public:
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wxOverlay();
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~wxOverlay();
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/**
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Clears the overlay without restoring the former state. To be done, for
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example, when the window content has been changed and repainted.
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*/
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void Reset();
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/**
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Sets or unsets constant opacity of the overlay window.
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If @a alpha is `-1`, use per-pixel alpha blending, otherwise use the
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given alpha value for all pixels.
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@note Drawing on the overlay window is opaque by default under wxMSW.
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You have to call SetOpacity(-1) before initializing the overlay and use
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a graphics context to do the actual drawing if you want per-pixel alpha
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blending. Or, assuming that SetOpacity(-1) wasn't called, explicitly set
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the alpha value (at any time) to change the overlay window's opacity.
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@note This is currently only implemented for wxMSW and does nothing in
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the other ports.
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@since 3.3.0
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*/
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void SetOpacity(int alpha);
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};
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/**
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@class wxDCOverlay
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Connects an overlay with a drawing DC.
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@library{wxcore}
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@see wxOverlay, wxDC
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*/
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class wxDCOverlay
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{
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public:
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/**
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Connects this overlay to the corresponding drawing dc, if the overlay is
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not initialized yet this call will do so.
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*/
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wxDCOverlay(wxOverlay &overlay, wxDC *dc, int x , int y , int width , int height);
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/**
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Convenience wrapper that behaves the same using the entire area of the dc.
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*/
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wxDCOverlay(wxOverlay &overlay, wxDC *dc);
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/**
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Removes the connection between the overlay and the dc.
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*/
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virtual ~wxDCOverlay();
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/**
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Clears the layer, restoring the state at the last init.
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*/
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void Clear();
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};
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