1wxMemoryDC(3)              Erlang Module Definition              wxMemoryDC(3)
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NAME

6       wxMemoryDC - Functions for wxMemoryDC class
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DESCRIPTION

9       A  memory  device context provides a means to draw graphics onto a bit‐
10       map. When drawing in to a mono-bitmap, using wxWHITE,  wxWHITE_PEN  and
11       wxWHITE_BRUSH  will  draw  the  background  colour (i.e. 0) whereas all
12       other colours will draw the foreground colour (i.e. 1).
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14       A bitmap must be selected into the new memory DC before it may be  used
15       for anything. Typical usage is as follows:
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17       Note  that the memory DC must be deleted (or the bitmap selected out of
18       it) before a bitmap can be reselected into another memory DC.
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20       And, before performing any other operations on  the  bitmap  data,  the
21       bitmap must be selected out of the memory DC:
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23       This happens automatically when wxMemoryDC object goes out of scope.
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25       See: wxBitmap, wxDC
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27       This class is derived (and can use functions) from: wxDC
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29       wxWidgets docs: wxMemoryDC
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DATA TYPES

32       wxMemoryDC() = wx:wx_object()
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EXPORTS

35       new() -> wxMemoryDC()
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37              Constructs a new memory device context.
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39              Use  the  wxDC:isOk/1 member to test whether the constructor was
40              successful in creating a usable device context. Don't forget  to
41              select a bitmap into the DC before drawing on it.
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43       new(Dc) -> wxMemoryDC()
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45              Types:
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47                 Dc = wxDC:wxDC() | wxBitmap:wxBitmap()
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49              Constructs  a  new memory device context having the same charac‐
50              teristics as the given existing device context.
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52              This constructor creates a memory device context compatible with
53              dc  in  wxMSW, the argument is ignored in the other ports. If dc
54              is NULL, a device context compatible with the screen is created,
55              just as with the default constructor.
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57       selectObject(This, Bitmap) -> ok
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59              Types:
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61                 This = wxMemoryDC()
62                 Bitmap = wxBitmap:wxBitmap()
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64              Works  exactly like selectObjectAsSource/2 but this is the func‐
65              tion you should use when you select a bitmap because you want to
66              modify it, e.g.
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68              drawing on this DC.
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70              Using selectObjectAsSource/2 when modifying the bitmap may incur
71              some problems related to wxBitmap being a reference counted  ob‐
72              ject (see overview_refcount).
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74              Before using the updated bitmap data, make sure to select it out
75              of context first either by selecting ?wxNullBitmap into the  de‐
76              vice context or destroying the device context entirely.
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78              If  the bitmap is already selected in this device context, noth‐
79              ing is done. If it is selected in another context, the  function
80              asserts and drawing on the bitmap won't work correctly.
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82              See: wxDC:drawBitmap/4
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84       selectObjectAsSource(This, Bitmap) -> ok
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86              Types:
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88                 This = wxMemoryDC()
89                 Bitmap = wxBitmap:wxBitmap()
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91              Selects  the given bitmap into the device context, to use as the
92              memory bitmap.
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94              Selecting the bitmap into a memory DC allows you  to  draw  into
95              the DC (and therefore the bitmap) and also to use wxDC:blit/6 to
96              copy the bitmap to a window. For  this  purpose,  you  may  find
97              wxDC:drawIcon/3 easier to use instead.
98
99              If  the  argument  is ?wxNullBitmap (or some other uninitialised
100              wxBitmap) the current bitmap is selected out of the device  con‐
101              text,  and  the  original  bitmap restored, allowing the current
102              bitmap to be destroyed safely.
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104       destroy(This :: wxMemoryDC()) -> ok
105
106              Destroys the object.
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110wxWidgets team.                     wx 2.1                       wxMemoryDC(3)