Shulou(Shulou.com)06/02 Report--

Description

The existing wxDC and all derived class-related device environments do not achieve anti-aliasing. After all, wxDC is only an encapsulation of CDC, and only GDI+ supports anti-aliasing.

The core reason for defining static variables such as rasterizer in the following code is that it allocates a large amount of memory when performing rendering calculations, which is easy to cause memory fragmentation, of course agg::pixfmt_bgra32 and agg::renderer_scanline_aa_solid

There is no memory allocation, but for the sake of unity, it is constructed as a static variable. in fact, the area pointed to by the applied rendering cache should also be set to static variables, and then by specifying width and height, memory fragmentation can be avoided to the maximum extent.

Code

Header file

# include "wx/wx.h"

# include "agg/agg_scanline_p.h"

# include "agg/agg_renderer_scanline.h"

# include "agg/agg_pixfmt_rgba.h"

# include "agg/agg_rasterizer_scanline_aa.h"

Struct PosCoordinate

{

Double x

Double y

}

Class CFlightInstrumentCompassCtrl: public wxControl

{

Private:

DECLARE_EVENT_TABLE ()

Public:

CFlightInstrumentCompassCtrl () {Init ();}

Void Init () {}

CFlightInstrumentCompassCtrl (wxWindow * parent

WxWindowID id

Const wxPoint& pos = wxDefaultPosition

Const wxSize& size = wxDefaultSize

Long style = 0

Const wxValidator& validator = wxDefaultValidator)

{

Init ()

Create (parent, id, pos, size, style, validator)

}

Bool Create (wxWindow * parent

WxWindowID id

Const wxPoint& pos = wxDefaultPosition

Const wxSize& size = wxDefaultSize

Long style = 0

Const wxValidator& validator = wxDefaultValidator)

~ CFlightInstrumentCompassCtrl (void)

Void SetCompassParameter (double leanAngle, double leanDistance, int rollAngle)

Void SetSize (wxSize size)

{

M_size = size

}

Private:

Void GetFitCircleInfo (double & circleRaduis, double & circleCenterX, double & circleCenterY)

Private:

Double m_arrowDiviationAngle

Double m_arrowAngle

Double m_leanDistance

Int m_curRollAngle

WxSize m_size

Protected:

Void OnPaint (wxPaintEvent& event)

Void OnEraseBackground (wxEraseEvent& event)

Public:

/ / declare a pair of AGG objects that need to be used, because they are static variables and need to be defined in the source file, otherwise there will be an unparsed external symbol error

Static agg::rendering_buffer m_rbuf

Static agg::pixfmt_bgra32 m_pixf

Static agg::renderer_base m_renb

Static agg::renderer_scanline_aa_solid m_ren

Static agg::rasterizer_scanline_aa m_ras

Static agg::scanline_p8 m_sl

}

Source file

# include "flightinstrumentcompass.h"

# include "wx/msw/window.h"

# include

# include "wx/dc.h"

BEGIN_EVENT_TABLE (CFlightInstrumentCompassCtrl, wxControl)

EVT_PAINT (CFlightInstrumentCompassCtrl::OnPaint)

EVT_ERASE_BACKGROUND (CFlightInstrumentCompassCtrl::OnEraseBackground)

END_EVENT_TABLE ()

/ / definition of static AGG object

Agg::rendering_buffer CFlightInstrumentCompassCtrl::m_rbuf

Agg::pixfmt_bgra32 CFlightInstrumentCompassCtrl::m_pixf

Agg::renderer_base CFlightInstrumentCompassCtrl::m_renb

Agg::renderer_scanline_aa_solid CFlightInstrumentCompassCtrl::m_ren

Agg::rasterizer_scanline_aa CFlightInstrumentCompassCtrl::m_ras

Agg::scanline_p8 CFlightInstrumentCompassCtrl::m_sl

Bool CFlightInstrumentCompassCtrl::Create (wxWindow * parent

WxWindowID id

Const wxPoint& pos

Const wxSize& size

Long style

Const wxValidator& validator)

{

If (! wxControl::Create (parent, id, pos, size, style, validator))

{

Return false

}

Return true

}

CFlightInstrumentCompassCtrl::~CFlightInstrumentCompassCtrl (void)

{

}

Void CFlightInstrumentCompassCtrl::OnPaint (wxPaintEvent& event)

{

WXHWND hWnd = GetHWND ()

PAINTSTRUCT ps

HDC hdc = BeginPaint (hWnd, & ps)

RECT rt

:: GetClientRect (hWnd, & rt)

Int width = rt.right-rt.left

Int height = rt.bottom-rt.top

BITMAPINFO bmp_info

Bmp_info.bmiHeader.biSize = sizeof (BITMAPINFOHEADER)

Bmp_info.bmiHeader.biWidth = width

Bmp_info.bmiHeader.biHeight = height

Bmp_info.bmiHeader.biPlanes = 1

Bmp_info.bmiHeader.biBitCount = 32

Bmp_info.bmiHeader.biCompression = BI_RGB

Bmp_info.bmiHeader.biSizeImage = 0

Bmp_info.bmiHeader.biXPelsPerMeter = 0

Bmp_info.bmiHeader.biYPelsPerMeter = 0

Bmp_info.bmiHeader.biClrUsed = 0

Bmp_info.bmiHeader.biClrImportant = 0

HDC mem_dc =:: CreateCompatibleDC (hdc)

Void* buf = 0

HBITMAP bmp =:: CreateDIBSection (

Mem_dc

& bmp_info

DIB_RGB_COLORS

& buf

0

0

);

/ / Selecting the object before doing anything allows you

/ / to use AGG together with native Windows GDI.

HBITMAP temp = (HBITMAP):: SelectObject (mem_dc, bmp)

/ / =

/ / AGG lowest level code.

M_rbuf.attach ((unsigned char*) buf, width, height,-width*4); / / Use negative stride in order

M_pixf.attach (m_rbuf)

M_renb.attach (m_pixf)

M_ren.attach (m_renb)

M_renb.clear (agg::rgba8 (255,255,255,255))

M_ras.move_to_d (20.7,34.15)

M_ras.line_to_d (398.23, 123.43)

M_ras.line_to_d (165.45, 401.87)

/ / Setting the attrribute (color) & Rendering

M_ren.color (agg::rgba8 (80,90,60))

Agg::render_scanlines (m_ras, m_sl, m_ren)

/ / =

/ /-

/ / Display the p_w_picpath. If the p_w_picpath is B-G-R-A (32-bits per pixel)

/ / one can use AlphaBlend instead of BitBlt. In case of AlphaBlend

/ / one also should clear the p_w_picpath with zero alpha, i.e. Rgba8 (0pr 0j0j0j0pl 0)

:: BitBlt (

Hdc

Rt.left

Rt.top

Width

Height

Mem_dc

0

0

SRCCOPY

);

/ / Free resources

:: SelectObject (mem_dc, temp)

:: DeleteObject (bmp)

:: DeleteObject (mem_dc)

EndPaint (hWnd, & ps)

Return

}

Be careful

1 in order to be able to use wxDC-derived classes such as wxClientDC, you need to include the header file wx/wx.h, otherwise the following compilation error occurs when calling DrawText to render fonts: DrawTextW is not a member of wxClientDC

2 after using AGG rendering, it is not necessary to use a derived class of wxDC for rendering. AGG rendering is to first build a bitmap, then finish rendering on this basis, and paste the image. If you want to use wxClientDC, it will cause flicker. If you use wxMemoryDC (also build a memory bitmap and then map it), you can only use the cropping function to map a certain area, and it is impossible to carry out mixed rendering, otherwise it will overwrite the existing rendering, and in the process of stretching the window, you will find that AGG rendering is successful. But wxClientDC and others can't see any rendering results.

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