76 lines
2.7 KiB
C
76 lines
2.7 KiB
C
//---
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// gint:display-cg - fxcg50 rendering functions
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//
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// This module covers all 16-bit opaque rendering functions. For
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// gamma-related functions, color composition, check out a color library.
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//
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// All the functions in this module work on a 396x224 resolution - gint
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// lets you use the full surface!
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//---
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#ifndef GINT_DISPLAY_CG
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#define GINT_DISPLAY_CG
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#ifdef FXCG50
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#include <gint/defs/types.h>
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/* Expose the VRAM variable if GINT_NEED_VRAM is defined. It must always point
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to a 32-aligned buffer of size 177408. Any function can use it freely to
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perform rendering or store data when not drawing. Triple buffering is
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already implemened in gint, see the dvram() function below.
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In this module, colors are in the 16-bit R5G6B5 format, as it is the format
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used by the display controller. */
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#ifdef GINT_NEED_VRAM
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extern uint16_t *vram;
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#endif
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/* Provide a platform-agnostic definition of color_t.
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Some functions also support transparency, in which case they take an [int]
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as argument and recognize negative values as transparent. */
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typedef uint16_t color_t;
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enum {
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color_none = -1,
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};
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//---
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// Video RAM management
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//---
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/* dvram() - Control video RAM address and triple buffering
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Normal rendering under gint uses double-buffering: there is one image
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displayed on the screen and one in memory, in a region called the video RAM
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(VRAM). The application draws frames in the VRAM then sends them to the
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screen only when they are finished, using dupdate().
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On fxcg50, the performance bottleneck is almost always the graphical
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rendering (especially in games) because the high amount of data, 173 kB per
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frame in full-resolution, makes graphics manipulation computationally
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expensive. The transfer also takes about 10 ms in itself.
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Since gint transfers data to the screen using the DMA, it is possible to run
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the application while the finished frame is being transferred. However,
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writing to the VRAM during this period it is still begin read by the DMA.
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Changing the contents of the VRAM too soon would alter the frame being sent.
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The solution to this is to use triple-buffering with the display and two
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VRAMs that are alternately begin written to while the other is being
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transferred. The VRAM switching is handled by dupdate() and is activated
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whenever two VRAMs are configured.
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By default gint uses triple buffering with one VRAM in the user stack and
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a second one in the system stack.
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VRAMs must be contiguous, 32-aligned, (2*396*224)-byte buffers.
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@main Main VRAM area, used alone if [secondary] is NULL
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@secondary Additional VRAM area, enables triple buffering if non-NULL */
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void dvram(uint16_t *main, uint16_t *secondary);
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#endif /* FXCG50 */
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#endif /* GINT_DISPLAY_CG */
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