libweston: Add pixel-format helpers
Rather than duplicating knowledge of pixel formats across several
components, create a custom central repository.
Signed-off-by: Daniel Stone <daniels@collabora.com>
[Pekka: fix include paths and two copy-pastas]
Reviewed-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
diff --git a/libweston/pixel-formats.h b/libweston/pixel-formats.h
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+++ b/libweston/pixel-formats.h
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+/*
+ * Copyright © 2016 Collabora, Ltd.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ *
+ * Author: Daniel Stone <daniels@collabora.com>
+ */
+
+#include <inttypes.h>
+#include <stdbool.h>
+
+/**
+ * Contains information about pixel formats, mapping format codes from
+ * wl_shm and drm_fourcc.h (which are deliberately identical, but for the
+ * special cases of WL_SHM_ARGB8888 and WL_SHM_XRGB8888) into various
+ * sets of information. Helper functions are provided for dealing with these
+ * raw structures.
+ */
+struct pixel_format_info {
+ /** DRM/wl_shm format code */
+ uint32_t format;
+
+ /** If non-zero, number of planes in base (non-modified) format. */
+ int num_planes;
+
+ /** If format contains alpha channel, opaque equivalent of format,
+ * i.e. alpha channel replaced with X. */
+ uint32_t opaque_substitute;
+
+ /** How the format should be sampled, expressed in terms of tokens
+ * from the EGL_WL_bind_wayland_display extension. If not set,
+ * assumed to be either RGB or RGBA, depending on whether or not
+ * the format contains an alpha channel. The samplers may still
+ * return alpha even for opaque formats; users must manually set
+ * the alpha channel to 1.0 (or ignore it) if the format is
+ * opaque. */
+ uint32_t sampler_type;
+
+ /** GL format, if data can be natively/directly uploaded. Note that
+ * whilst DRM formats are little-endian unless explicitly specified,
+ * (i.e. DRM_FORMAT_ARGB8888 is stored BGRA as sequential bytes in
+ * memory), GL uses the sequential byte order, so that format maps to
+ * GL_BGRA_EXT plus GL_UNSIGNED_BYTE. To add to the confusion, the
+ * explicitly-sized types (e.g. GL_UNSIGNED_SHORT_5_5_5_1) read in
+ * machine-endian order, so for these types, the correspondence
+ * depends on endianness. */
+ int gl_format;
+
+ /** GL data type, if data can be natively/directly uploaded. */
+ int gl_type;
+
+ /** If set, this format can be used with the legacy drmModeAddFB()
+ * function (not AddFB2), using this and the bpp member. */
+ int depth;
+
+ /** See 'depth' member above. */
+ int bpp;
+
+ /** Horizontal subsampling; if non-zero, divide the width by this
+ * member to obtain the number of columns in the source buffer for
+ * secondary planes only. Stride is not affected by horizontal
+ * subsampling. */
+ int hsub;
+
+ /** Vertical subsampling; if non-zero, divide the height by this
+ * member to obtain the number of rows in the source buffer for
+ * secondary planes only. */
+ int vsub;
+
+ /* Ordering of chroma components. */
+ enum {
+ ORDER_UV = 0,
+ ORDER_VU,
+ } chroma_order;
+
+ /* If packed YUV (num_planes == 1), ordering of luma/chroma
+ * components. */
+ enum {
+ ORDER_LUMA_CHROMA = 0,
+ ORDER_CHROMA_LUMA,
+ } luma_chroma_order;
+};
+
+/**
+ * Get pixel format information for a DRM format code
+ *
+ * Given a DRM format code, return a pixel format info structure describing
+ * the properties of that format.
+ *
+ * @param format DRM format code to get info for
+ * @returns A pixel format structure (must not be freed), or NULL if the
+ * format could not be found
+ */
+const struct pixel_format_info *pixel_format_get_info(uint32_t format);
+
+/**
+ * Get number of planes used by a pixel format
+ *
+ * Given a pixel format info structure, return the number of planes
+ * required for a buffer. Note that this is not necessarily identical to
+ * the number of samplers required to be bound, as two views into a single
+ * plane are sometimes required.
+ *
+ * @param format Pixel format info structure
+ * @returns Number of planes required for the format
+ */
+unsigned int
+pixel_format_get_plane_count(const struct pixel_format_info *format);
+
+/**
+ * Determine if a pixel format is opaque or contains alpha
+ *
+ * Returns whether or not the pixel format is opaque, or contains a
+ * significant alpha channel. Note that the suggested EGL sampler type may
+ * still sample undefined data into the alpha channel; users must consider
+ * alpha as 1.0 if the format is opaque, and not rely on the sampler to
+ * return this when sampling from the alpha channel.
+ *
+ * @param format Pixel format info structure
+ * @returns True if the format is opaque, or false if it has significant alpha
+ */
+bool pixel_format_is_opaque(const struct pixel_format_info *format);
+
+/**
+ * Get compatible opaque equivalent for a format
+ *
+ * Given a pixel format info structure, return a format which is wholly
+ * compatible with the input format, but opaque, ignoring the alpha channel.
+ * If an alpha format is provided, but the content is known to all be opaque,
+ * then this can be used as a substitute to avoid blending.
+ *
+ * If the input format is opaque, this function will return the input format.
+ *
+ * @param format Pixel format info structure
+ * @returns A pixel format info structure for the compatible opaque substitute
+ */
+const struct pixel_format_info *
+pixel_format_get_opaque_substitute(const struct pixel_format_info *format);
+
+/**
+ * Return the effective sampling width for a given plane
+ *
+ * When horizontal subsampling is effective, a sampler bound to a secondary
+ * plane must bind the sampler with a smaller effective width. This function
+ * returns the effective width to use for the sampler, i.e. dividing by hsub.
+ *
+ * If horizontal subsampling is not in effect, this will be equal to the
+ * width.
+ *
+ * @param format Pixel format info structure
+ * @param plane Zero-indexed plane number
+ * @param width Width of the buffer
+ * @returns Effective width for sampling
+ */
+unsigned int
+pixel_format_width_for_plane(const struct pixel_format_info *format,
+ unsigned int plane,
+ unsigned int width);
+
+/**
+ * Return the effective sampling height for a given plane
+ *
+ * When vertical subsampling is in effect, a sampler bound to a secondary
+ * plane must bind the sampler with a smaller effective height. This function
+ * returns the effective height to use for the sampler, i.e. dividing by vsub.
+ *
+ * If vertical subsampling is not in effect, this will be equal to the height.
+ *
+ * @param format Pixel format info structure
+ * @param plane Zero-indexed plane number
+ * @param height Height of the buffer
+ * @returns Effective width for sampling
+ */
+unsigned int
+pixel_format_height_for_plane(const struct pixel_format_info *format,
+ unsigned int plane,
+ unsigned int height);