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Name
ANGLE_window_fixed_size
Name Strings
EGL_ANGLE_window_fixed_size
Contributors
John Bauman
Shannon Woods
Geoff Lang
Contacts
John Bauman, Google Inc. (jbauman 'at' google.com)
Status
Complete
Version
Version 5, July 23, 2018
Number
EGL Extension #??
Dependencies
This extension is written against the wording of the EGL 1.4
Specification.
Overview
This extension allows creating a window surface that does not resize
automatically.
New Types
None
New Procedures and Functions
None
New Tokens
Accepted by the <attribute> parameter of eglQuerySurface and by the
<attrib_list> parameter of eglCreateWindowSurface:
EGL_FIXED_SIZE_ANGLE 0x3201
Additions to Chapter 3 of the EGL 1.4 Specification:
Modify the third paragraph of Section 3.5.1 (Creating On-Screen Rendering
Surfaces)
"<attrib_list> specifies a list of attributes for the window. The list has
the same structure as described for eglChooseConfig. Attributes that can
be specified in <attrib_list> include EGL_RENDER_BUFFER,
EGL_VG_COLORSPACE, EGL_VG_ALPHA_FORMAT, EGL_FIXED_SIZE_ANGLE, EGL_WIDTH,
and EGL_HEIGHT."
Add before the last paragraph of Section 3.5.1
"EGL_FIXED_SIZE_ANGLE specifies whether the surface must be resized by the
implementation when the native window is resized. The default value is
EGL_FALSE. Its value can be EGL_TRUE, in which case the size must be
specified when the window is created, or EGL_FALSE, in which case the size
is taken from the native window. Its default value is EGL_FALSE.
If the value of EGL_FIXED_SIZE_ANGLE is EGL_TRUE, the window surface's
size in pixels is specified by the EGL_WIDTH and EGL_HEIGHT attributes.
If its value is EGL_FALSE, then the values of EGL_WIDTH and EGL_HEIGHT
are ignored and the window surface must be resized by the implementation
subsequent to the native window being resized, and prior to copying its
contents to the native window (e.g. in eglSwapBuffers, as described in
section 3.9.1.1). The default values for EGL_WIDTH and EGL_HEIGHT are zero.
If the value specified for either of EGL_WIDTH or EGL_HEIGHT is less than
zero then an EGL_BAD_PARAMETER error is generated."
Add the following entry to Table 3.5
(Queryable surface attributes and types)
Attribute Type Description
-------------------- ------- ---------------------------------------------
EGL_FIXED_SIZE_ANGLE boolean Surface will not be resized with a native
window
Replace the last paragraph on page 37 in Section 3.5.6 (Surface Attributes)
"Querying EGL_WIDTH and EGL_HEIGHT returns respectively the width and
height, in pixels, of the surface. For a pixmap surface or window surface
with EGL_FIXED_SIZE_ANGLE set to EGL_FALSE, these values are initially
equal to the width and height of the native window or pixmap with respect
to which the surface was created. If the native window is resized and the
corresponding window surface is not fixed size, the corresponding window
surface will eventually be resized by the implementation to match (as
discussed in section 3.9.1). If there is a discrepancy because EGL has not
yet resized the window surface, the size returned by eglQuerySurface will
always be that of the EGL surface, not the corresponding native window."
Alter the beginning of the first paragraph of Section 3.5.6 (Surface
Attributes)
"The specified attribute of surface is set to value. Attributes that can
be specified are EGL_MIPMAP_LEVEL, EGL_MULTISAMPLE_RESOLVE,
EGL_SWAP_BEHAVIOR, EGL_WIDTH, and EGL_HEIGHT."
Add the following paragraph to Section 3.5.6 (Surface Attributes)
"If attribute is EGL_WIDTH or EGL_HEIGHT then the value specifies the new
surface width or height respectively. The new width and height are not
guarenteed to be applied until the next call to eglSwapBuffers or
eglWaitNative. If the surface does not have EGL_FIXED_SIZE_ANGLE set then
an EGL_BAD_MATCH error is generated."
Add the following paragraph to Section 3.5.6 (Surface Attributes)
"Querying EGL_FIXED_SIZE_ANGLE returns EGL_FALSE if the surface will be
resized to match a native window, and EGL_TRUE if the surface cannot be
resized."
Alter the beginning of the first paragraph of Section 3.9.1.1 (Native
Window Resizing)
"If the surface has EGL_FIXED_SIZE_ANGLE set and EGL_WIDTH or EGL_HEIGHT
have changed or the surface does not have EGL_FIXED_SIZE_ANGLE set and its
corresponding native window has been resized prior to the swap, surface
must be resized to match".
Issues
1. Should there be a way to resize a window surface that had its size
specified initially.
RESOLVED: No. Surfaces that have their sizes specified initially must have
EGL_FIXED_SIZE_ANGLE set and can never be resized.
RESOLVED(rev 5): Fixed size surfaces can now be resized by setting
EGL_WIDTH and EGL_HEIGHT surface attributes. This is the best way to give
users explicit control of the size of window surfaces without re-creating
them on each resize.
Revision History
Version 5, 2018/07/23 - Allow reizing fixed size surfaces.
Version 4, 2014/02/24 - formatting changes.
Version 3, 2014/02/12 - ignore EGL_WIDTH and EGL_HEIGHT if
EGL_FIXED_SIZE_ANGLE is EGL_FALSE
Version 2, 2014/02/07 - rename to EGL_ANGLE_window_fixed_size, and add an
EGL_FIXED_SIZE_ANGLE token.
Version 1, 2014/02/05 - first draft.
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