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62 lines
2.7 KiB
Markdown
62 lines
2.7 KiB
Markdown
The [CLS](CLS) statement clears the [_DEST](_DEST).
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## Syntax
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> [CLS](CLS) [method%] [, bgColor&]
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## Parameter(s)
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* method% specifies which parts of the page to clear, and can have one of the following values:
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* CLS - clears the active graphics or text viewport or the entire text screen and refreshes bottom function [KEY LIST](KEY-LIST) line.
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* CLS 0 - Clears the entire page of text and graphics. Print cursor is moved to row 1 at column 1.
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* CLS 1 - Clears only the graphics view port. Has no effect for text mode.
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* CLS 2 - Clears only the text view port. The print cursor is moved to the top row of the text view port at column 1.
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* The bgColor& specifies the color attribute or palette index to use when clearing the screen in **QB64**.
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## Description
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* In legacy [SCREEN](SCREEN) modes bgColor& specifies the color attribute of the background.
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* For 32-bit graphics mode, bgColor& specifies the [_RGB](_RGB) or [_RGBA](_RGBA) color to use.
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* **32-bit screen surface backgrounds (black) have zero [_ALPHA](_ALPHA) so that they are transparent when placed over other surfaces.**
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* Use [CLS](CLS) or [_DONTBLEND](_DONTBLEND) to make a new surface background [_ALPHA](_ALPHA) 255 or opaque.
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* If not specified, bgColor& is assumed to be the current background color. 32-bit backgrounds will change to opaque.
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* If bgColor& is not a valid attribute, an [ERROR Codes](ERROR-Codes) error will occur.
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* Use [_PRINTMODE](_PRINTMODE) to allow the background colors to be visible through the text or the text background.
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## Example(s)
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Printing black text on a white background in QB64.
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```vb
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SCREEN 12
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CLS , 15
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_PRINTMODE _KEEPBACKGROUND 'keeps the text background visible
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COLOR 0: PRINT "This is black text on a white background!"
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K$ = INPUT$(1)
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```
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> *Explanation:* [_PRINTMODE](_PRINTMODE) can be used with [PRINT](PRINT) or [_PRINTSTRING](_PRINTSTRING) to make the text or the text background transparent.
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You don't need to do anything special to use a .PNG image with alpha/transparency. Here's a simple example:
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```vb
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SCREEN _NEWIMAGE(640, 480, 32)
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CLS , _RGB(0, 255, 0)
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i = _LOADIMAGE(**"qb64_trans.png"**) 'see note below examples to get the image
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_PUTIMAGE (0, 0), i 'places image at upper left corner of window w/o stretching it
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```
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> *Explanation:* When QB64 loads a .PNG file containing a transparent color, that color will be properly treated as transparent when _PUTIMAGE is used to put it onto another image. You can use a .PNG file containing transparency information in a 256-color screen mode in QB64. [CLS](CLS) sets the [_CLEARCOLOR](_CLEARCOLOR) setting using [_RGB](_RGB).
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## See Also
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* [SCREEN](SCREEN)
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* [_RGB](_RGB), [_RGBA](_RGBA), [_RGB32](_RGB32), [_RGBA32](_RGBA32)
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* [VIEW PRINT](VIEW-PRINT), [VIEW](VIEW)
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* [_CLEARCOLOR](_CLEARCOLOR)
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