icon_cache.c File Reference

Icon store. A small cache that maps a resource id to its picture and is shared across a face, so each icon loads once and is freed in one place. Also carries the palette tint and the auto-trim margin scan. More...

#include "ui/icon_cache.h"
#include <string.h>

Data Structures
struct	IconEntry
	One cached icon. Its resource id, the loaded picture, and the extra state icon_tint and the auto-trim scan keep between calls. More...

Macros
#define	ICON_CACHE_MAX   24
	How many distinct icons the cache holds at once.

Functions
void	icon_tint (GBitmap *bmp, GColor color)
	Paints an icon a different colour. It only works on icons saved as little colour-table pictures. Other kinds it just leaves alone. The see-through pixels stay see-through so the edges keep looking clean.
static uint8_t	px_alpha (GBitmapFormat fmt, const uint8_t *data, const GColor *palette, int x)
	Alpha of a single pixel, 0 to 3, across the bitmap formats the colour platforms produce.
IconMargins	icon_margins_of (GBitmap *bmp)
	Measures the transparent margins of any bitmap, for icons that live outside the shared cache such as a weather picture that reloads as the weather changes. All zero when auto-trim is off or the bitmap is NULL.
static IconEntry *	icon_entry (uint32_t res)
	Finds or loads the cache entry for a resource id.
GBitmap *	icon_get (uint32_t res)
	Hands back an icon picture from the cache, loading it the first time it is asked for.
IconMargins	icon_margins (uint32_t res)
	The measured transparent margins of a cached icon. Loads and measures it the first time, then returns the cached numbers. All zero when auto-trim is off or the icon could not load.
GSize	icon_size (uint32_t res)
	The size of an icon in pixels. Gives back GSize(0,0) if it could not load.
void	icon_align_trim (GAlign align, IconMargins m, int *trim_dx, int *trim_dy)
	The extra offset that pins the opaque box rather than the full bitmap at a given anchor. A right or bottom edge kills the trailing margin. A left or top edge kills the leading one. A centred axis splits the difference so the visible art centres.
void	icons_cleanup (void)
	Frees every icon picture in the cache.

Variables
static IconEntry	s_cache [ICON_CACHE_MAX]
	The cached icons.
static uint8_t	s_cache_count
	How many cache entries are in use.
static uint32_t	s_use_clock
	Ticks once per lookup and gets stamped onto whichever entry was touched.

Detailed Description

Icon store. A small cache that maps a resource id to its picture and is shared across a face, so each icon loads once and is freed in one place. Also carries the palette tint and the auto-trim margin scan.

Macro Definition Documentation

ICON_CACHE_MAX

#define ICON_CACHE_MAX   24

How many distinct icons the cache holds at once.

It has to cover every icon one redraw touches. A busy layout, two eight column forecast strips with a pair of two icon panels under them, touches 20, so 24 leaves a little room. Past that the cache still works but thrashes. A redraw walks its icons in the same order every time, so the coldest entry is always the next one wanted, and every lookup reloads the resource and rescans its margins. A reload that fails on a busy heap leaves that icon blank.

Icons nothing draws any more, such as the moon glyphs of days gone by, are what gets dropped. A face that draws more at once sets its own cap in its appinfo's defines.

Function Documentation

icon_entry()

IconEntry * icon_entry ( uint32_t res )

static

Finds or loads the cache entry for a resource id.

One scan feeds icon_get, icon_margins, and icon_size, so a caller that reads more than one of them on every panel repaint does not re-scan the same icon for each.

Parameters

res	The resource id.

Returns

The cache entry, or NULL when the icon can't be cached.

px_alpha()

uint8_t px_alpha ( GBitmapFormat fmt, const uint8_t * data, const GColor * palette, int x )

static

Alpha of a single pixel, 0 to 3, across the bitmap formats the colour platforms produce.

A GColor8 keeps alpha in its top 2 bits, and colour-table pixels index a GColor8 palette. Colour-table pixels pack MSB first, so the leftmost pixel sits in the high-order bits.

Parameters

fmt	The bitmap's pixel format.
data	The row's raw pixel bytes.
palette	The bitmap's colour palette, for a colour-table format.
x	The pixel's column within the row.

Returns

The pixel's alpha, 0 (fully see-through) to 3 (fully opaque).

Variable Documentation

s_use_clock

uint32_t s_use_clock

static

Ticks once per lookup and gets stamped onto whichever entry was touched.

The entry holding the lowest stamp is the one nothing has wanted for the longest.