1. Graphic Device Interface
GDI/GDI+
Graphic Device Interface

2. What it is? It enables applications to use graphics
It do not access the graphics hardware directly
interacts with device drivers
More or less obsolete (Direct2D)

3. Before we go... WM_PAINT!
is sent when the system or another application makes a request to paint a portion of an application's window
UpdateWindow
RedrawWindow
InvalidateRect

4. Device Context
is a structure that defines a set of graphic objects and their associated attributes, as well as the graphic modes that affect output
Device independence - applications can draw and print output on a variety of devices
Gdi.dll
Device driver

5. DC functions BeginPaint GetDC GetCompatibleDC
GetCurrentObject -> GetObject
GetStockObject
SelectObject
Etc...

6. Principles When you want to draw a line, you are using Pen
When you want to color something, you are using Brush
It is possible to use multiple pens and brushes, but only one at a time
SelectObject

7. Pen LineTo Polyline TextOut Etc... PS_SOLID PS_DASH PS_DOT PS_DASHDOT
HPEN CreatePen(
_In_ int fnPenStyle,
_In_ int nWidth,
_In_ COLORREF crColor);
PS_SOLID
PS_DASH
PS_DOT
PS_DASHDOT
PS_DASHDOTDOT
PS_NULL
PS_INSIDEFRAME
LineTo
Polyline
TextOut
Etc...

8. Brush CreateHatchBrush CreatePatternBrush Etc… Ellipse Polygon
HBRUSH CreateSolidBrush(
_In_ COLORREF crColor );
CreateHatchBrush
CreatePatternBrush
Etc…
Ellipse
Polygon
Rectangle
Etc...

9. Bitmaps Device context is needed Capturing or displaying bitmap
CreateCompatibleDC
Capturing or displaying bitmap
CreateCompatibleBitmap
BitBlt
StretchBlt

10. Clipping
is the process of limiting output to a region or path within the client area of an application window
A clipping region is a region with edges that are either straight lines or curves
A clip path is a region with edges that are straight lines, Bézier curves, or combinations of both

11. Using Clipping (I) Create clip path BeginPath/EndPath RGN_AND RGN_COPY
RGN_DIFF
RGN_OR
RGN_XOR
BOOL SelectClipPath(
_In_ HDC hdc,
_In_ int iMode);

12. Using Clipping (II) Functions NULLREGION SIMPLEREGION COMPLEXREGION
int SelectClipRgn(
_In_ HDC hdc,
_In_ HRGN hrgn );
Functions
CombineRgn
CreatePolygonRgn
CreateRectRgn
Etc…
NULLREGION
SIMPLEREGION
COMPLEXREGION
ERROR

13. Coordinate Spaces and Transformations
Drawing with predefined units
Centering
Scaling
Translating
Rotating
Shearing
Reflecting
SetGraphicsMode
SetMapMode
SetWorldTransform
XFORM

15. Other possibilities Fonts and texts Metafiles
Multiple display monitors

16. Clear your mess Keep and restore old values Release drawing handles
Select Object
DeleteObject
Release drawing handles
EndPaint
ReleaseDC