ScreenControl

FreeBASIC

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ScreenControl
 
Sets or gets internal graphics library settings

Syntax

Declare Sub ScreenControl ( ByVal what As Long, ByRef param1 As Integer = 0, ByRef param2 As Integer = 0, ByRef param3 As Integer = 0, ByRef param4 As Integer = 0 )
Declare Sub ScreenControl ( ByVal what As Long, ByRef param As String = "" )

Usage

ScreenControl( what [, [ param1 ][, [ param2 ][, [ param3 ][, [ param4 ]]]]] )
or,
ScreenControl( what [, param ] )

Parameters

what
specifies the function to perform
param1
optional first integer parameter, contains value to be set on entry or value got on exit
param2
optional second integer parameter, contains value to be set on entry or value got on exit
param3
optional third integer parameter, contains value to be set on entry or value got on exit
param4
optional fourth integer parameter, contains value to be set on entry or value got on exit
param
optional string parameter, contains text to be set on entry or text got on exit

Description


This function can be used to set or get internal GfxLib states. The what parameter specifies which operation to perform. On operations that set states, the param* parameters must contain the values to be set. On operations that get states, param* will hold the values returned by GfxLib when the function returns.
The meaning of the param* parameters depend on the what parameter, whose possible values are defined as constants in fbgfx.bi. In lang fb, they are set to be stored in the FB Namespace.
Below is a list of the supported what constants - and their values as defined at time of writing - along with the parameters associated with them.

Supported operations
Note: * denotes operations that are allowed while a graphics mode has not yet been set via Screen (Graphics) or ScreenRes. For all other operations, return values are zero(0) or the empty string("") and the operation has no effect if a graphics mode is not available at call time.

Get operations
  • GET_WINDOW_POS (0) Returns the current window position, in desktop coordinates.
[OUT] param1 x
[OUT] param2 y
  • * GET_WINDOW_TITLE (1) Returns the title of the program window.
[OUT] param title
  • GET_WINDOW_HANDLE (2) Returns a handle to the program window.
[OUT] param1 handle; this is a HWND in Windows, a "Window" XID in X11
  • * GET_DESKTOP_SIZE (3) Returns the desktop size, in pixels.
[OUT] param1 width
[OUT] param2 height
  • GET_SCREEN_SIZE (4) Returns the current screen size in pixels.
[OUT] param1 width
[OUT] param2 height
  • GET_SCREEN_DEPTH (5) Returns current graphics mode screen depth.
[OUT] param1 bits per pixel
  • GET_SCREEN_BPP (6) Returns current graphics mode BPP.
[OUT] param1 bytes per pixel
  • GET_SCREEN_PITCH (7) Returns the current graphics mode framebuffer pitch, in bytes.
[OUT] param1 pitch
  • GET_SCREEN_REFRESH (8) Returns the current graphics mode refresh rate, in hertz.
[OUT] param1 rate
  • GET_DRIVER_NAME (9) Returns the current graphics mode driver name.
[OUT] param name
  • GET_TRANSPARENT_COLOR (10) Returns the transparent color value for the current graphics mode depth.
[OUT] param1 value
  • GET_VIEWPORT (11) Returns the current viewport as set by the View (Graphics) statement, in screen coordinates.
[OUT] param1 x1
[OUT] param2 y1
[OUT] param3 x2
[OUT] param4 y2
  • GET_PEN_POS (12) Returns the last graphical pen position, in screen coordinates. This position is used in graphics functions supporting relative coordinates using the Step keyword.
[OUT] param1 x
[OUT] param2 y
  • GET_COLOR (13) Returns the current graphics mode color.
[OUT] param1 foreground
[OUT] param2 background
  • GET_ALPHA_PRIMITIVES (14) Returns if primitives drawing support for alpha channel is enabled.
[OUT] param1 TRUE (-1) if alpha primitives is enabled, FALSE (0) otherwise
  • GET_GL_EXTENSIONS (15) Returns a string holding all supported GL extensions, or the empty string if not in OpenGL mode.
[OUT] param supported GL extensions
  • GET_HIGH_PRIORITY (16) Returns if GFX_HIGH_PRIORITY was specified in the flags passed to Screen or ScreenRes.
[OUT] param1 higher priority graphics processing enabled

Set operations
  • SET_WINDOW_POS (100) Sets the current program window position, in desktop coordinates.
[IN] param1 x
[IN] param2 y
  • * SET_WINDOW_TITLE (101) Sets the current program window title. This is equivalent to calling WindowTitle( param ).
[IN] param title
  • SET_PEN_POS (102) Sets the current graphical pen position, in screen coordinates. This position is used in graphics functions supporting relative coordinates using the Step keyword.
[IN] param1 x
[IN] param2 y
  • * SET_DRIVER_NAME (103) Sets the name of the internal graphics driver to be used in subsequent calls to Screen or ScreenRes.
[IN] param driver name
  • SET_ALPHA_PRIMITIVES (104) Sets if primitives drawing should honor alpha channel.
[IN] param1 enabled
  • * SET_GL_COLOR_BITS (105) Sets the number of bits dedicated to the OpenGL color buffer
[IN] param1 bits
  • * SET_GL_COLOR_RED_BITS (106) Sets the number of bits dedicated to the red component of the OpenGL color buffer
[IN] param1 bits
  • * SET_GL_COLOR_GREEN_BITS (107) Sets the number of bits dedicated to the green component of the OpenGL color buffer
[IN] param1 bits
  • * SET_GL_COLOR_BLUE_BITS (108) Sets the number of bits dedicated to the blue component of the OpenGL color buffer
[IN] param1 bits
  • * SET_GL_COLOR_ALPHA_BITS (109) Sets the number of bits dedicated to the alpha component of the OpenGL color buffer
[IN] param1 bits
  • * SET_GL_DEPTH_BITS (110) Sets the number of bits dedicated to the OpenGL depth buffer
[IN] param1 bits
  • * SET_GL_STENCIL_BITS (111) Sets the number of bits dedicated to the OpenGL stencil buffer
[IN] param1 bits
  • * SET_GL_ACCUM_BITS (112) Sets the number of bits dedicated to the OpenGL accumulation buffer
[IN] param1 bits
  • * SET_GL_ACCUM_RED_BITS (113) Sets the number of bits dedicated to the red component of the OpenGL accumulation buffer
[IN] param1 bits
  • * SET_GL_ACCUM_GREEN_BITS (114) Sets the number of bits dedicated to the green component of the OpenGL accumulation buffer
[IN] param1 bits
  • * SET_GL_ACCUM_BLUE_BITS (115) Sets the number of bits dedicated to the blue component of the OpenGL accumulation buffer
[IN] param1 bits
  • * SET_GL_ACCUM_ALPHA_BITS (116) Sets the number of bits dedicated to the alpha component of the OpenGL accumulation buffer
[IN] param1 bits
  • * SET_GL_NUM_SAMPLES (117) Sets the number of samples to be used for OpenGL multisampling
[IN] param1 samples

Other operations
  • POLL_EVENTS (200) Cause the library to poll all events, ie to check the system event queue, specifically used for retrieving keyboard and mouse events. This is most useful for OpenGL code where Flip is not used, as normally Flip will cause these events to be polled.

Example

'' include fbgfx.bi for some useful definitions
#include "fbgfx.bi"

'' use FB namespace for easy access to types/constants
Using FB

Dim e As EVENT
Dim As Integer x0, y0, x, y
Dim As Integer shakes = 0
Dim As Any Ptr img

ScreenRes 320, 200, 32
Print "Click to shake window"

'' find window coordinates
ScreenControl GET_WINDOW_POS, x0, y0

Do

    If (shakes > 0) Then
        
        '' do a shake of the window

        If (shakes > 1) Then

            '' move window to a random position near its original coordinates
            x = x0 + Int(32 * (Rnd() - 0.5))
            y = y0 + Int(32 * (Rnd() - 0.5))
            ScreenControl SET_WINDOW_POS, x, y

        Else

            '' move window back to its original coordinates
            ScreenControl SET_WINDOW_POS, x0, y0

        End If

        shakes -= 1

    End If

    If (ScreenEvent(@e)) Then
        Select Case e.type
        
        '' user pressed the mouse button
        Case EVENT_MOUSE_BUTTON_PRESS

            If (shakes = 0) Then
                '' set to do 20 shakes
                shakes = 20

                '' find current window coordinates to shake around
                ScreenControl GET_WINDOW_POS, x0, y0
            End If

        '' user closed the window or pressed a key
        Case EVENT_WINDOW_CLOSE, EVENT_KEY_PRESS
            '' exit to end of program
            Exit Do

        End Select
    End If

    '' free up CPU for other programs
    Sleep 5

Loop


'' include fbgfx.bi for some useful definitions
#include "fbgfx.bi"

Dim As String driver

#ifdef __FB_WIN32__
'' set graphics driver to GDI (Win32 only), before calling ScreenRes
ScreenControl FB.SET_DRIVER_NAME, "GDI"
#endif

ScreenRes 640, 480

'' fetch graphics driver name and display it to user
ScreenControl FB.GET_DRIVER_NAME, driver
Print "Graphics driver name: " & driver

'' wait for a keypress before closing the window
Sleep


Dialect Differences

  • Not available in the -lang qb dialect unless referenced with the alias __Screencontrol.

Differences from QB

  • New to FreeBASIC

See also

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