ScreenRes

FreeBASIC

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ScreenRes

Initializes a graphics mode by specifying horizontal and vertical resolution

Syntax

Declare Function ScreenRes ( ByVal width As Long, ByVal height As Long, ByVal depth As Long = 8, ByVal num_pages As Long = 1, ByVal flags As Long = 0, ByVal refresh_rate As Long = 0 ) As Long

Usage

ScreenRes width, height [, [depth] [, [num_pages] [, [flags] [, refresh_rate ]]]] result = ScreenRes( width, height [, [depth] [, [num_pages] [, [flags] [, refresh_rate ]]]] )

Parameters

width, height

The display width and height, respectively. For fullscreen mode, the user should check the availability of the resolution using ScreenList.

depth

The color depth in bits per pixel. Valid color depths are: 1, 2, 4, 8, 16 and 32. Values of 15 and 24 are also allowed as aliases for 16 and 32, respectively. If omitted, the default is 8 bits per pixel. 8 bits and below will give a palette image. The default palette will be the first 2 ^ depth colors of the 256-color palette used in Screen 13.

num_pages

The number of video pages to create, defaults to 1. (see below)

flags

Used to set various properties of the screen, including fullscreen mode and the graphics driver used. (see below or the standard header "fbgfx.bi" for available flags)

refresh_rate

The desired refresh rate of the screen, only has an effect for fullscreen modes, and some systems and drivers only. Defaults to an appropriate value, invalid refresh rates will be ignored.

Return Value

Returns zero (0) if successful, or a non-zero error code to indicate a failure. (throws a runtime error) (???)

Description

ScreenRes tells the compiler to link the GfxLib and initializes a QB-only, QB-on-GUI or OpenGL graphics mode, depending on the flags setting

ScreenRes clears the created window or the full screen. In non-fullscreen modes, the resolution does not have to match any resolution of the graphics card. Resolutions like 555x111 are possible, GfxLib will create a window of such size. See the page GfxLib overview for DOS issues.

The font size in ScreenRes modes is set to 8x8 by default. This can be changed by setting the number of text rows/columns, using the Width function.

In QB-only modes a dumb window or fullscreen resolution is set, one or more buffers in standard memory are created, console commands are redirected to their graphic versions, a default palette is set and an automatic screen refresh thread is started. QB-like graphics and console statements can be used.

In QB-on-GUI modes one or more buffers in standard memory are created, console commands are redirected to their graphic versions and a default palette is set. QB-like graphics and console statements can be used. It is up to the user to create a window and to refresh it with the contents of the graphics buffers.

In OpenGL modes a dumb window or fullscreen resolution is set, one or more buffers in standard memory are created, and the system's OpenGL library is initialized. From here only OpenGL commands can be used to write to the graphics buffer. QB-like and console commands are forbidden. This mode allows to initialize OpenGL in a portable way.

flags details:

If flags are omitted, FreeBASIC uses QB-compatible graphics in windowed (except in DOS) mode. These constants are defined in fbgfx.bi. In the -lang fb dialect, these constants are part of the FB Namespace. Their values can be combined to form a mask using Operator Or. Note that most of the flags are not supported in DOS.

Available flags:

graphic mode flags

GFX_NULL: Starts a QB-on-GUI graphics mode. It creates a graphics buffer but not a window. User must implement the window, the events manager and refresh the screen as needed. This mode allows to mix FreeBASIC drawing functions with API-driven windows. Alternatively, it allows to process graphics (for example files) without making it visible on the screen, even in a purely console application. This flag overrides all other mode flags. See an Example of GFX_NULL in Windows.
GFX_OPENGL: Initializes OpenGL to draw in a dumb window. FreeBASIC graphic functions can't be used. The screen is not automatically updated, Flip must be used. This option provides a portable way to initialize the OpenGL Library.
If none of the above options is specified, FreeBASIC enters the QB-only graphics mode: it creates a buffer and a dumb window and sets a thread that automatically updates the screen and manages keyboard and mouse. The FreeBASIC drawing functions can be used.

window mode flags

Window mode flags are meaningless if GFX_NULL mode is used
GFX_WINDOWED: If windowed mode is supported, FreeBASIC opens a window of the requested size in the present desktop
GFX_FULLSCREEN: The graphics card switch mode is switched to the requested mode and color depth and OS fullscreen mode is used. If the mode is not available in the present card FreeBASIC switches to windowed mode.
If GFX_FULLSCREEN is not specified, the behavior for GFX_WINDOWED is assumed.
GFX_NO_SWITCH: Prevents the user from changing to fullscreen or to windowed mode by pressing Alt-Enter.
GFX_NO_FRAME: Creates a window without a border.
GFX_SHAPED_WINDOW: Creates transparent regions wherever RGBA(255, 0, 255, 0) is drawn on the screen.
GFX_ALWAYS_ON_TOP: Creates a window that stays always on top.

option flags

Flags working in any mode, they activate special behaviors
GFX_ALPHA_PRIMITIVES: Tells the graphics library to enable alpha channel support for all drawing primitives. This means the alpha specified in a color value (via either the RGBA macro or direct color in the form &h;AARRGGBB) will always be used by all primitives.
GFX_HIGH_PRIORITY: Tells the graphics library to enable a higher priority for graphics processing. Only has an effect on gdi and DirectX drivers on Win32 platform.

OpenGL Buffer flags

These flags work only in OpenGL graphics mode, must be combined with GFX_OPENGL
GFX_STENCIL_BUFFER: Forces OpenGL to use Stencil buffer
GFX_ACCUMULATION_BUFFER: Forces OpenGL to use Accumulation buffer
GFX_MULTISAMPLE: Requests fullscreen anti-aliasing through the ARB_multisample extension

Depending on whether the GFX_FULLSCREEN parameter is present or not, Screen will try to set the specified video mode in fullscreen or windowed mode, respectively. If fullscreen mode is set and the system cannot set specified mode in fullscreen, it will try in windowed mode. If windowed mode is set and the system fails to open a window for specified mode, it will try fullscreen. If everything fails, Screen will have no effect and execution will resume from the statement following the Screen call. You should take care of checking if a graphics mode has been set or not, and behave accordingly; a way to check if Screen is successful is to test the return value of the ScreenPtr function; see its page for details.

Graphics mode console
Console commands (Locate, Print), input can be used both with standard QB Screen modes and with the extended ones too, provided the standard color depth is not modified by using the second argument of Screen. Where the table says more than one text resolution is available for the text mode, the required text resolution can be requested by using Width. Any characters Printed will erase the background around them; it does not use a transparent background.

Example

' Set the screen mode to 320*200, with 8 bits per pixel ScreenRes 320, 200, 8 ' Draw color bands in a diagonal pattern over the whole screen For y As Integer = 0 To 200-1 For x As Integer = 0 To 320-1 PSet (x,y),(x + y) And 255 Next x Next y ' Display the text "Hello World!!" over the lines we've drawn, in the top-left hand corner Print "Hello world!!" ' Keep the window open until the user presses a key Sleep

Platform Differences

In DOS, Windowing and OpenGL related switches are not available, and other issues, see GfxLib overview

Dialect Differences

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

Differences from QB

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