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switched to a simplified generated gl binding that should work with both regular GL and GLES

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This commit is contained in:
Thomas Friedel 2019-02-24 13:28:50 +01:00
parent 222c12142a
commit 549a6f2c2e
14 changed files with 8519 additions and 16 deletions
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2
backend/gogl/clip.go
View file

@ -3,7 +3,7 @@ package goglbackend
import (
"unsafe"
"github.com/go-gl/gl/v3.2-core/gl"
"github.com/tfriedel6/canvas/backend/gogl/gl"
)
func (b *GoGLBackend) ClearClip() {

2
backend/gogl/fill.go
View file

@ -5,8 +5,8 @@ import (
"math"
"unsafe"
"github.com/go-gl/gl/v3.2-core/gl"
"github.com/tfriedel6/canvas/backend/backendbase"
"github.com/tfriedel6/canvas/backend/gogl/gl"
)
func (b *GoGLBackend) Clear(pts [4][2]float64) {

109
backend/gogl/gl/conversions.go Normal file
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@ -0,0 +1,109 @@
// Code generated by glow (https://github.com/go-gl/glow). DO NOT EDIT.
package gl
import (
"fmt"
"reflect"
"strings"
"unsafe"
)
// #include <stdlib.h>
import "C"
// Ptr takes a slice or pointer (to a singular scalar value or the first
// element of an array or slice) and returns its GL-compatible address.
//
// For example:
//
// var data []uint8
// ...
// gl.TexImage2D(gl.TEXTURE_2D, ..., gl.UNSIGNED_BYTE, gl.Ptr(&data[0]))
func Ptr(data interface{}) unsafe.Pointer {
if data == nil {
return unsafe.Pointer(nil)
}
var addr unsafe.Pointer
v := reflect.ValueOf(data)
switch v.Type().Kind() {
case reflect.Ptr:
e := v.Elem()
switch e.Kind() {
case
reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64,
reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64,
reflect.Float32, reflect.Float64:
addr = unsafe.Pointer(e.UnsafeAddr())
default:
panic(fmt.Errorf("unsupported pointer to type %s; must be a slice or pointer to a singular scalar value or the first element of an array or slice", e.Kind()))
}
case reflect.Uintptr:
addr = unsafe.Pointer(v.Pointer())
case reflect.Slice:
addr = unsafe.Pointer(v.Index(0).UnsafeAddr())
default:
panic(fmt.Errorf("unsupported type %s; must be a slice or pointer to a singular scalar value or the first element of an array or slice", v.Type()))
}
return addr
}
// PtrOffset takes a pointer offset and returns a GL-compatible pointer.
// Useful for functions such as glVertexAttribPointer that take pointer
// parameters indicating an offset rather than an absolute memory address.
func PtrOffset(offset int) unsafe.Pointer {
return unsafe.Pointer(uintptr(offset))
}
// Str takes a null-terminated Go string and returns its GL-compatible address.
// This function reaches into Go string storage in an unsafe way so the caller
// must ensure the string is not garbage collected.
func Str(str string) *uint8 {
if !strings.HasSuffix(str, "\x00") {
panic("str argument missing null terminator: " + str)
}
header := (*reflect.StringHeader)(unsafe.Pointer(&str))
return (*uint8)(unsafe.Pointer(header.Data))
}
// GoStr takes a null-terminated string returned by OpenGL and constructs a
// corresponding Go string.
func GoStr(cstr *uint8) string {
return C.GoString((*C.char)(unsafe.Pointer(cstr)))
}
// Strs takes a list of Go strings (with or without null-termination) and
// returns their C counterpart.
//
// The returned free function must be called once you are done using the strings
// in order to free the memory.
//
// If no strings are provided as a parameter this function will panic.
func Strs(strs ...string) (cstrs **uint8, free func()) {
if len(strs) == 0 {
panic("Strs: expected at least 1 string")
}
// Allocate a contiguous array large enough to hold all the strings' contents.
n := 0
for i := range strs {
n += len(strs[i])
}
data := C.malloc(C.size_t(n))
// Copy all the strings into data.
dataSlice := *(*[]byte)(unsafe.Pointer(&reflect.SliceHeader{
Data: uintptr(data),
Len: n,
Cap: n,
}))
css := make([]*uint8, len(strs)) // Populated with pointers to each string.
offset := 0
for i := range strs {
copy(dataSlice[offset:offset+len(strs[i])], strs[i][:]) // Copy strs[i] into proper data location.
css[i] = (*uint8)(unsafe.Pointer(&dataSlice[offset])) // Set a pointer to it.
offset += len(strs[i])
}
return (**uint8)(&css[0]), func() { C.free(data) }
}

282
backend/gogl/gl/khrplatform.h Normal file
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@ -0,0 +1,282 @@
#ifndef __khrplatform_h_
#define __khrplatform_h_
/*
** Copyright (c) 2008-2009 The Khronos Group Inc.
**
** Permission is hereby granted, free of charge, to any person obtaining a
** copy of this software and/or associated documentation files (the
** "Materials"), to deal in the Materials without restriction, including
** without limitation the rights to use, copy, modify, merge, publish,
** distribute, sublicense, and/or sell copies of the Materials, and to
** permit persons to whom the Materials are furnished to do so, subject to
** the following conditions:
**
** The above copyright notice and this permission notice shall be included
** in all copies or substantial portions of the Materials.
**
** THE MATERIALS ARE 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
** MATERIALS OR THE USE OR OTHER DEALINGS IN THE MATERIALS.
*/
/* Khronos platform-specific types and definitions.
*
* $Revision: 23298 $ on $Date: 2013-09-30 17:07:13 -0700 (Mon, 30 Sep 2013) $
*
* Adopters may modify this file to suit their platform. Adopters are
* encouraged to submit platform specific modifications to the Khronos
* group so that they can be included in future versions of this file.
* Please submit changes by sending them to the public Khronos Bugzilla
* (http://khronos.org/bugzilla) by filing a bug against product
* "Khronos (general)" component "Registry".
*
* A predefined template which fills in some of the bug fields can be
* reached using http://tinyurl.com/khrplatform-h-bugreport, but you
* must create a Bugzilla login first.
*
*
* See the Implementer's Guidelines for information about where this file
* should be located on your system and for more details of its use:
* http://www.khronos.org/registry/implementers_guide.pdf
*
* This file should be included as
* #include <KHR/khrplatform.h>
* by Khronos client API header files that use its types and defines.
*
* The types in khrplatform.h should only be used to define API-specific types.
*
* Types defined in khrplatform.h:
* khronos_int8_t signed 8 bit
* khronos_uint8_t unsigned 8 bit
* khronos_int16_t signed 16 bit
* khronos_uint16_t unsigned 16 bit
* khronos_int32_t signed 32 bit
* khronos_uint32_t unsigned 32 bit
* khronos_int64_t signed 64 bit
* khronos_uint64_t unsigned 64 bit
* khronos_intptr_t signed same number of bits as a pointer
* khronos_uintptr_t unsigned same number of bits as a pointer
* khronos_ssize_t signed size
* khronos_usize_t unsigned size
* khronos_float_t signed 32 bit floating point
* khronos_time_ns_t unsigned 64 bit time in nanoseconds
* khronos_utime_nanoseconds_t unsigned time interval or absolute time in
* nanoseconds
* khronos_stime_nanoseconds_t signed time interval in nanoseconds
* khronos_boolean_enum_t enumerated boolean type. This should
* only be used as a base type when a client API's boolean type is
* an enum. Client APIs which use an integer or other type for
* booleans cannot use this as the base type for their boolean.
*
* Tokens defined in khrplatform.h:
*
* KHRONOS_FALSE, KHRONOS_TRUE Enumerated boolean false/true values.
*
* KHRONOS_SUPPORT_INT64 is 1 if 64 bit integers are supported; otherwise 0.
* KHRONOS_SUPPORT_FLOAT is 1 if floats are supported; otherwise 0.
*
* Calling convention macros defined in this file:
* KHRONOS_APICALL
* KHRONOS_APIENTRY
* KHRONOS_APIATTRIBUTES
*
* These may be used in function prototypes as:
*
* KHRONOS_APICALL void KHRONOS_APIENTRY funcname(
* int arg1,
* int arg2) KHRONOS_APIATTRIBUTES;
*/
/*-------------------------------------------------------------------------
* Definition of KHRONOS_APICALL
*-------------------------------------------------------------------------
* This precedes the return type of the function in the function prototype.
*/
#if defined(_WIN32) && !defined(__SCITECH_SNAP__)
# define KHRONOS_APICALL __declspec(dllimport)
#elif defined (__SYMBIAN32__)
# define KHRONOS_APICALL IMPORT_C
#else
# define KHRONOS_APICALL
#endif
/*-------------------------------------------------------------------------
* Definition of KHRONOS_APIENTRY
*-------------------------------------------------------------------------
* This follows the return type of the function and precedes the function
* name in the function prototype.
*/
#if defined(_WIN32) && !defined(_WIN32_WCE) && !defined(__SCITECH_SNAP__)
/* Win32 but not WinCE */
# define KHRONOS_APIENTRY __stdcall
#else
# define KHRONOS_APIENTRY
#endif
/*-------------------------------------------------------------------------
* Definition of KHRONOS_APIATTRIBUTES
*-------------------------------------------------------------------------
* This follows the closing parenthesis of the function prototype arguments.
*/
#if defined (__ARMCC_2__)
#define KHRONOS_APIATTRIBUTES __softfp
#else
#define KHRONOS_APIATTRIBUTES
#endif
/*-------------------------------------------------------------------------
* basic type definitions
*-----------------------------------------------------------------------*/
#if (defined(__STDC_VERSION__) && __STDC_VERSION__ >= 199901L) || defined(__GNUC__) || defined(__SCO__) || defined(__USLC__)
/*
* Using <stdint.h>
*/
#include <stdint.h>
typedef int32_t khronos_int32_t;
typedef uint32_t khronos_uint32_t;
typedef int64_t khronos_int64_t;
typedef uint64_t khronos_uint64_t;
#define KHRONOS_SUPPORT_INT64 1
#define KHRONOS_SUPPORT_FLOAT 1
#elif defined(__VMS ) || defined(__sgi)
/*
* Using <inttypes.h>
*/
#include <inttypes.h>
typedef int32_t khronos_int32_t;
typedef uint32_t khronos_uint32_t;
typedef int64_t khronos_int64_t;
typedef uint64_t khronos_uint64_t;
#define KHRONOS_SUPPORT_INT64 1
#define KHRONOS_SUPPORT_FLOAT 1
#elif defined(_WIN32) && !defined(__SCITECH_SNAP__)
/*
* Win32
*/
typedef __int32 khronos_int32_t;
typedef unsigned __int32 khronos_uint32_t;
typedef __int64 khronos_int64_t;
typedef unsigned __int64 khronos_uint64_t;
#define KHRONOS_SUPPORT_INT64 1
#define KHRONOS_SUPPORT_FLOAT 1
#elif defined(__sun__) || defined(__digital__)
/*
* Sun or Digital
*/
typedef int khronos_int32_t;
typedef unsigned int khronos_uint32_t;
#if defined(__arch64__) || defined(_LP64)
typedef long int khronos_int64_t;
typedef unsigned long int khronos_uint64_t;
#else
typedef long long int khronos_int64_t;
typedef unsigned long long int khronos_uint64_t;
#endif /* __arch64__ */
#define KHRONOS_SUPPORT_INT64 1
#define KHRONOS_SUPPORT_FLOAT 1
#elif 0
/*
* Hypothetical platform with no float or int64 support
*/
typedef int khronos_int32_t;
typedef unsigned int khronos_uint32_t;
#define KHRONOS_SUPPORT_INT64 0
#define KHRONOS_SUPPORT_FLOAT 0
#else
/*
* Generic fallback
*/
#include <stdint.h>
typedef int32_t khronos_int32_t;
typedef uint32_t khronos_uint32_t;
typedef int64_t khronos_int64_t;
typedef uint64_t khronos_uint64_t;
#define KHRONOS_SUPPORT_INT64 1
#define KHRONOS_SUPPORT_FLOAT 1
#endif
/*
* Types that are (so far) the same on all platforms
*/
typedef signed char khronos_int8_t;
typedef unsigned char khronos_uint8_t;
typedef signed short int khronos_int16_t;
typedef unsigned short int khronos_uint16_t;
/*
* Types that differ between LLP64 and LP64 architectures - in LLP64,
* pointers are 64 bits, but 'long' is still 32 bits. Win64 appears
* to be the only LLP64 architecture in current use.
*/
#ifdef _WIN64
typedef signed long long int khronos_intptr_t;
typedef unsigned long long int khronos_uintptr_t;
typedef signed long long int khronos_ssize_t;
typedef unsigned long long int khronos_usize_t;
#else
typedef signed long int khronos_intptr_t;
typedef unsigned long int khronos_uintptr_t;
typedef signed long int khronos_ssize_t;
typedef unsigned long int khronos_usize_t;
#endif
#if KHRONOS_SUPPORT_FLOAT
/*
* Float type
*/
typedef float khronos_float_t;
#endif
#if KHRONOS_SUPPORT_INT64
/* Time types
*
* These types can be used to represent a time interval in nanoseconds or
* an absolute Unadjusted System Time. Unadjusted System Time is the number
* of nanoseconds since some arbitrary system event (e.g. since the last
* time the system booted). The Unadjusted System Time is an unsigned
* 64 bit value that wraps back to 0 every 584 years. Time intervals
* may be either signed or unsigned.
*/
typedef khronos_uint64_t khronos_utime_nanoseconds_t;
typedef khronos_int64_t khronos_stime_nanoseconds_t;
#endif
/*
* Dummy value used to pad enum types to 32 bits.
*/
#ifndef KHRONOS_MAX_ENUM
#define KHRONOS_MAX_ENUM 0x7FFFFFFF
#endif
/*
* Enumerated boolean type
*
* Values other than zero should be considered to be true. Therefore
* comparisons should not be made against KHRONOS_TRUE.
*/
typedef enum {
KHRONOS_FALSE = 0,
KHRONOS_TRUE = 1,
KHRONOS_BOOLEAN_ENUM_FORCE_SIZE = KHRONOS_MAX_ENUM
} khronos_boolean_enum_t;
#endif /* __khrplatform_h_ */

8041
backend/gogl/gl/package.go Normal file
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File diff suppressed because it is too large Load diff

71
backend/gogl/gl/procaddr.go Normal file
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@ -0,0 +1,71 @@
// Code generated by glow (https://github.com/go-gl/glow). DO NOT EDIT.
// This file implements GlowGetProcAddress for every supported platform. The
// correct version is chosen automatically based on build tags:
//
// windows: WGL
// darwin: CGL
// linux freebsd: GLX
//
// Use of EGL instead of the platform's default (listed above) is made possible
// via the "egl" build tag.
//
// It is also possible to install your own function outside this package for
// retrieving OpenGL function pointers, to do this see InitWithProcAddrFunc.
package gl
/*
#cgo windows CFLAGS: -DTAG_WINDOWS
#cgo windows LDFLAGS: -lopengl32
#cgo darwin CFLAGS: -DTAG_DARWIN
#cgo darwin LDFLAGS: -framework OpenGL
#cgo linux freebsd CFLAGS: -DTAG_POSIX
#cgo linux freebsd LDFLAGS: -lGL
#cgo egl CFLAGS: -DTAG_EGL
#cgo egl LDFLAGS: -lEGL
// Check the EGL tag first as it takes priority over the platform's default
// configuration of WGL/GLX/CGL.
#if defined(TAG_EGL)
#include <stdlib.h>
#include <EGL/egl.h>
void* GlowGetProcAddress_glglesunion(const char* name) {
return eglGetProcAddress(name);
}
#elif defined(TAG_WINDOWS)
#define WIN32_LEAN_AND_MEAN 1
#include <windows.h>
#include <stdlib.h>
static HMODULE ogl32dll = NULL;
void* GlowGetProcAddress_glglesunion(const char* name) {
void* pf = wglGetProcAddress((LPCSTR) name);
if (pf) {
return pf;
}
if (ogl32dll == NULL) {
ogl32dll = LoadLibraryA("opengl32.dll");
}
return GetProcAddress(ogl32dll, (LPCSTR) name);
}
#elif defined(TAG_DARWIN)
#include <stdlib.h>
#include <dlfcn.h>
void* GlowGetProcAddress_glglesunion(const char* name) {
return dlsym(RTLD_DEFAULT, name);
}
#elif defined(TAG_POSIX)
#include <stdlib.h>
#include <GL/glx.h>
void* GlowGetProcAddress_glglesunion(const char* name) {
return glXGetProcAddress((const GLubyte *) name);
}
#endif
*/
import "C"
import "unsafe"
func getProcAddress(namea string) unsafe.Pointer {
cname := C.CString(namea)
defer C.free(unsafe.Pointer(cname))
return C.GlowGetProcAddress_glglesunion(cname)
}

6
backend/gogl/gogl.go
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@ -5,8 +5,8 @@ import (
"image/color"
"math"
"github.com/go-gl/gl/v3.2-core/gl"
"github.com/tfriedel6/canvas/backend/backendbase"
"github.com/tfriedel6/canvas/backend/gogl/gl"
)
const alphaTexSize = 2048
@ -447,8 +447,8 @@ func (b *GoGLBackend) enableTextureRenderTarget(offscr *offscreenBuffer) {
gl.GenRenderbuffers(1, &offscr.renderStencilBuf)
gl.BindRenderbuffer(gl.RENDERBUFFER, offscr.renderStencilBuf)
gl.RenderbufferStorage(gl.RENDERBUFFER, gl.DEPTH24_STENCIL8, int32(b.w), int32(b.h))
gl.FramebufferRenderbuffer(gl.FRAMEBUFFER, gl.DEPTH_STENCIL_ATTACHMENT, gl.RENDERBUFFER, offscr.renderStencilBuf)
gl.RenderbufferStorage(gl.RENDERBUFFER, gl.STENCIL_INDEX8, int32(b.w), int32(b.h))
gl.FramebufferRenderbuffer(gl.FRAMEBUFFER, gl.STENCIL_ATTACHMENT, gl.RENDERBUFFER, offscr.renderStencilBuf)
gl.FramebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, offscr.tex, 0)

2
backend/gogl/gradients.go
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@ -3,8 +3,8 @@ package goglbackend
import (
"runtime"
"github.com/go-gl/gl/v3.2-core/gl"
"github.com/tfriedel6/canvas/backend/backendbase"
"github.com/tfriedel6/canvas/backend/gogl/gl"
)
// LinearGradient is a gradient with any number of

2
backend/gogl/imagedata.go
View file

@ -5,7 +5,7 @@ import (
"image/color"
"unsafe"
"github.com/go-gl/gl/v3.2-core/gl"
"github.com/tfriedel6/canvas/backend/gogl/gl"
)
// GetImageData returns an RGBA image of the current image

6
backend/gogl/images.go
View file

@ -6,8 +6,8 @@ import (
"runtime"
"unsafe"
"github.com/go-gl/gl/v3.2-core/gl"
"github.com/tfriedel6/canvas/backend/backendbase"
"github.com/tfriedel6/canvas/backend/gogl/gl"
)
// Image represents a loaded image that can be used in various drawing functions
@ -124,7 +124,7 @@ func loadImageGray(src *image.Gray, tex uint32) (*Image, error) {
return nil, err
}
if src.Stride == img.w {
gl.TexImage2D(gl.TEXTURE_2D, 0, gl.RED, int32(img.w), int32(img.h), 0, gl.RED, gl.UNSIGNED_BYTE, gl.Ptr(&src.Pix[0]))
gl.TexImage2D(gl.TEXTURE_2D, 0, gl.ALPHA, int32(img.w), int32(img.h), 0, gl.ALPHA, gl.UNSIGNED_BYTE, gl.Ptr(&src.Pix[0]))
} else {
data := make([]uint8, 0, img.w*img.h)
for y := 0; y < img.h; y++ {
@ -132,7 +132,7 @@ func loadImageGray(src *image.Gray, tex uint32) (*Image, error) {
end := start + img.w
data = append(data, src.Pix[start:end]...)
}
gl.TexImage2D(gl.TEXTURE_2D, 0, gl.RED, int32(img.w), int32(img.h), 0, gl.RED, gl.UNSIGNED_BYTE, gl.Ptr(&data[0]))
gl.TexImage2D(gl.TEXTURE_2D, 0, gl.ALPHA, int32(img.w), int32(img.h), 0, gl.ALPHA, gl.UNSIGNED_BYTE, gl.Ptr(&data[0]))
}
if err := glError(); err != nil {
return nil, err

2
backend/gogl/shader.go
View file

@ -8,7 +8,7 @@ import (
"unicode"
"unicode/utf8"
"github.com/go-gl/gl/v3.2-core/gl"
"github.com/tfriedel6/canvas/backend/gogl/gl"
)
type shaderProgram struct {

2
backend/xmobile/gen/gen.go
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@ -73,7 +73,7 @@ func main() {
func rewrite(filename, src string) (string, string) {
src = strings.Replace(src, `package goglbackend`, `package xmobilebackend`, 1)
src = strings.Replace(src, `"github.com/go-gl/gl/v3.2-core/gl"`, `"golang.org/x/mobile/gl"`, 1)
src = strings.Replace(src, `"github.com/tfriedel6/canvas/backend/gogl/gl"`, `"golang.org/x/mobile/gl"`, 1)
src = strings.Replace(src, "\tgl.", "\tb.glctx.", -1)
src = strings.Replace(src, "GoGLBackend", "XMobileBackend", -1)
src = strings.Replace(src, "uint32(gl.TRIANGLES)", "gl.Enum(gl.TRIANGLES)", -1)

4
backend/xmobile/images.go
View file

@ -124,7 +124,7 @@ func loadImageGray(b *XMobileBackend, src *image.Gray, tex gl.Texture) (*Image,
return nil, err
}
if src.Stride == img.w {
b.glctx.TexImage2D(gl.TEXTURE_2D, 0, gl.RED, img.w, img.h, gl.RED, gl.UNSIGNED_BYTE, src.Pix[0:])
b.glctx.TexImage2D(gl.TEXTURE_2D, 0, gl.ALPHA, img.w, img.h, gl.ALPHA, gl.UNSIGNED_BYTE, src.Pix[0:])
} else {
data := make([]uint8, 0, img.w*img.h)
for y := 0; y < img.h; y++ {
@ -132,7 +132,7 @@ func loadImageGray(b *XMobileBackend, src *image.Gray, tex gl.Texture) (*Image,
end := start + img.w
data = append(data, src.Pix[start:end]...)
}
b.glctx.TexImage2D(gl.TEXTURE_2D, 0, gl.RED, img.w, img.h, gl.RED, gl.UNSIGNED_BYTE, data[0:])
b.glctx.TexImage2D(gl.TEXTURE_2D, 0, gl.ALPHA, img.w, img.h, gl.ALPHA, gl.UNSIGNED_BYTE, data[0:])
}
if err := glError(b); err != nil {
return nil, err

4
backend/xmobile/xmobile.go
View file

@ -450,8 +450,8 @@ func (b *XMobileBackend) enableTextureRenderTarget(offscr *offscreenBuffer) {
offscr.renderStencilBuf = b.glctx.CreateRenderbuffer()
b.glctx.BindRenderbuffer(gl.RENDERBUFFER, offscr.renderStencilBuf)
b.glctx.RenderbufferStorage(gl.RENDERBUFFER, gl.DEPTH24_STENCIL8, b.w, b.h)
b.glctx.FramebufferRenderbuffer(gl.FRAMEBUFFER, gl.DEPTH_STENCIL_ATTACHMENT, gl.RENDERBUFFER, offscr.renderStencilBuf)
b.glctx.RenderbufferStorage(gl.RENDERBUFFER, gl.STENCIL_INDEX8, b.w, b.h)
b.glctx.FramebufferRenderbuffer(gl.FRAMEBUFFER, gl.STENCIL_ATTACHMENT, gl.RENDERBUFFER, offscr.renderStencilBuf)
b.glctx.FramebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, offscr.tex, 0)