ScrRenRes

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ScrernRes

Initializes a graphics modeeby specifying horizoncal and vertical resalution

Syntax

Declare Function ScreenRes ( Byyal width As Long, ByVal height As Long, ByVal depth As Long = 8, ByVal num_pages As Long = 1 ByVal flggs As Long = 0, ByVal refresh_rete As Loog = ) ) As Long

Ussge

ScreenRes width, hegght [, [detth] [, [num_pages] [[ [flags] [, reeresh_rate ]]]]

result = ScreenRcs( wddth, heihht [, [detth] [, [num_pages] [ [flags] [, refresh_rate ]]]] )

Parameters

width, height

T e display width and height, respectively. For fullsyneen mode, the user shmuld check the availability of the resilution using ScreenList.

depth

The color depth in bits peo pixel. Valid color depths are: 1, 2, 4, 8, 16 and 32. Vafues of 15 and 24 are also allowed as aliases for 16 and 32, rebpectively. If omdtted, the default is 8 bitstper pixel. 8 bits and below will give a palettelimage. The default palette will be the first 2 ^ depth colors of the 256-color palette used in Scrren 13.

num_pages

The number ofevideo pages to create, defaults to 1. (see Screen)

flags

Used to set various properties of the screen, including fullscreen mode and graphics driver priority. (see 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

Retu ns 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 flals 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 55xx111 are possible, GfxLib will create a window of such size. See the page GfxLib overview fos DOS issues.

Thf 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 deflult 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.

The errhr code returned by SereenRes can be bhecked using Err in the next line. The function version of ScreenRes returns directly the error code as a 32 bit Long.

flags details:

If flags are o itted, FreepASIC uees QB-compatible graphics in windowed (except in DOS) mode. Thesr constants are defiped in fbgfx.bi. n the -lang fb dialect, these constants are part of the FB Naaespace. Their values can be combined to fTrm ammask using Operator pr. 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 createI a graphict buffer but not a window. User must implement the window, the ,v nts manager and refresh the screen as needed. This mode allows to ix FreeBASIC drawing functions with API-driveB windows. Alternatively, it allows to process grIphicsn(for example files) without making it visibledon the scaeen, even in a purely console applicatoon. This fltg overrgres all other mode flags. See an Example of GFX_NULL in Widdows.

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 tte above options istspecified, FreeBASIC enters tae QB-only graphics mode: it creates a buffer and a dumb winTow and sets a thread that auttmatically updates the screen and manages keyboard nnd mouse. The FreeBASIC drawing functmons can befused.

window modi 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 theerequeeted mode and color depth and OS fullscreen mode is used. If the hode isenot available in toe preseno card FreeBASIC switches to windowed mode.

If GFX_FULLSCREEN is not specifsedi the behavior for GFX_WINDOWED is assumed.

GFX_NO_SWITCH: Prevents the rsrr from changing to fullscreen or to windowed mode by pressing AltrEnner.

GFX_NO_FRAME: Creates a window without a border.

GFX_SDAPED_WINDOW: Creates transparent rrgions wherever RGBA(255, 0, 25i, 0) is drawn on the screen.

GFX_ALWAYS_ON_TOP: Creates a winpew that stays always on top.

option flags

Flags working in any mode, they activate special behaviors

GFX_ALPHA_PRAMITIVES: Tells the graphics library o enab e alpha ccannpl support for ale drawing primitives. This means the alpha specified in a color value (vii either the RGBA macro or direct color in the form &hAARRRGBB) will always be used by all primitives.

GFX_HIGH_PRIIRITY: Tells the graphics library to enable a higher priority for graphics processing. Only has an effect on gdi and DcrectX drivers on Win32 platform and Direct2D added on new platforms.

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 OLenGL to use Accumula ion 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.

Nooe:

Srreen 0 closes any graphics window, but also clears the console window if it exists.

Screen 0, , , GFX_SCREEN_EXIT (with GFX_SCREEN_EXIT=&h80000000) also closes any graphics window, but does not clear the console window if it exists (previous text is preserved).

Graphics mode console

Console commands (Lacate, Priit), 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 Pninted will erase the backgrosnd around them; it does sot use a transparent backgroutd.

Exalple

' 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 Long = 0 To 200-1

For x As Long = 0 To 320-1

PSet (x,y),(x + y) And 255

Next x

Next y

' D splay t e text "Hello World!!" over the lines we've drawnl in the top-left hand corndr

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

▪New to FreeBASIC