50 lines
1.6 KiB
C
50 lines
1.6 KiB
C
#ifndef _INTERNALS_DISPLAY_H
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#define _INTERNALS_DISPLAY_H
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#include <stdint.h>
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#include <stddef.h>
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extern uint32_t *vram;
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//---
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// Rectangle masks.
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//
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// The concept of 'rectangle masks' is used several times in this module.
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// It relies on the fact that operations affecting a rectangle act the
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// same for all lines, and line operation is very optimized. A rectangle
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// mask is a set of integers, where each bit indicate whether a specific
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// pixel is affected (1) by the operation, or not (0).
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//
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// For example to clear a rectangle such as (14, 16, 112, 48), the masks
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// will need to hold 0003ffff ffffffff ffffffff ffff0000. Bitwise-
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// combining them with video ram long entries yields very good performance
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// as compared to operation on single pixels. Each bitwise operation will
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// produce different results, which is very flexible.
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//
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// This technique can also be used in subtle cases with patterns more
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// complicated than rectangles, but within this module this is unlikely to
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// happen.
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//---
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/*
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adjustRectangle()
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Adjusts the given rectangle coordinates to ensure that :
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- the rectangle is entirely contained in the screen;
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- x1 < x2;
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- y1 < y2,
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which is needed when working with screen rectangles. Returns non-zero
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if the rectangle is outside the screen, which usually means there is
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nothing to do.
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*/
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int adjustRectangle(int *x1, int *y1, int *x2, int *y2);
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/*
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getMasks()
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Computes the rectangle masks needed to affect pixels located between x1
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and x2 (both included). The four masks are stored in the third argument
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(seen as an array).
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*/
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void getMasks(size_t x1, size_t x2, uint32_t *masks);
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#endif // _INTERNALS_DISPLAY_H
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