graphicsdriver/opengl: Enable to bind multiple textures (in theory)

internal/graphicsdriver/opengl/context_desktop.go

@@ -198,6 +198,13 @@ func (c *context) framebufferPixels(f *framebuffer, width, height int) ([]byte,
 	return pixels, nil
 }
 
+func (c *context) activeTexture(idx int) {
+	_ = c.t.Call(func() error {
+		gl.ActiveTexture(gl.TEXTURE0 + uint32(idx))
+		return nil
+	})
+}
+
 func (c *context) bindTextureImpl(t textureNative) {
 	_ = c.t.Call(func() error {
 		gl.BindTexture(gl.TEXTURE_2D, uint32(t))

internal/graphicsdriver/opengl/context_js.go

@@ -112,6 +112,8 @@ var (
 	unsignedByte        js.Value
 	unsignedShort       js.Value
 
+	texture0 int
+
 	isWebGL2Available bool
 )
 
@@ -154,6 +156,7 @@ func init() {
 	nearest = contextPrototype.Get("NEAREST")
 	noError = contextPrototype.Get("NO_ERROR")
 	rgba = contextPrototype.Get("RGBA")
+	texture0 = contextPrototype.Get("TEXTURE0").Int()
 	texture2d = contextPrototype.Get("TEXTURE_2D")
 	textureMagFilter = contextPrototype.Get("TEXTURE_MAG_FILTER")
 	textureMinFilter = contextPrototype.Get("TEXTURE_MIN_FILTER")
@@ -279,6 +282,12 @@ func (c *context) framebufferPixels(f *framebuffer, width, height int) ([]byte,
 	return jsutil.Uint8ArrayToSlice(p), nil
 }
 
+func (c *context) activeTexture(idx int) {
+	c.ensureGL()
+	gl := c.gl
+	gl.Call("activeTexture", texture0+idx)
+}
+
 func (c *context) bindTextureImpl(t textureNative) {
 	c.ensureGL()
 	gl := c.gl

internal/graphicsdriver/opengl/context_mobile.go

@@ -156,6 +156,11 @@ func (c *context) framebufferPixels(f *framebuffer, width, height int) ([]byte,
 	return pixels, nil
 }
 
+func (c *context) activeTexture(idx int) {
+	gl := c.gl
+	gl.ActiveTexture(mgl.Enum(mgl.TEXTURE0 + idx))
+}
+
 func (c *context) bindTextureImpl(t textureNative) {
 	gl := c.gl
 	gl.BindTexture(mgl.TEXTURE_2D, mgl.Texture(t))

internal/graphicsdriver/opengl/gl/package.go

@@ -49,6 +49,7 @@ const (
 	NO_ERROR             = 0
 	READ_WRITE           = 0x88BA
 	RGBA                 = 0x1908
+	TEXTURE0             = 0x84C0
 	TEXTURE_2D           = 0x0DE1
 	TEXTURE_MAG_FILTER   = 0x2800
 	TEXTURE_MIN_FILTER   = 0x2801

internal/graphicsdriver/opengl/gl/package_notwindows.go

@@ -95,7 +95,8 @@ package gl
 // typedef void (APIENTRY *GLDEBUGPROCAMD)(GLuint id,GLenum category,GLenum severity,GLsizei length,const GLchar *message,void *userParam);
 // typedef unsigned short GLhalfNV;
 // typedef GLintptr GLvdpauSurfaceNV;
-// typedef void (APIENTRY *GLVULKANPROCNV)(void);
+//
+// typedef void  (APIENTRYP GPACTIVETEXTURE)(GLenum  texture);
 // typedef void  (APIENTRYP GPATTACHSHADER)(GLuint  program, GLuint  shader);
 // typedef void  (APIENTRYP GPBINDATTRIBLOCATION)(GLuint  program, GLuint  index, const GLchar * name);
 // typedef void  (APIENTRYP GPBINDBUFFER)(GLenum  target, GLuint  buffer);
@@ -159,6 +160,9 @@ package gl
 // typedef void  (APIENTRYP GPVERTEXATTRIBPOINTER)(GLuint  index, GLint  size, GLenum  type, GLboolean  normalized, GLsizei  stride, const uintptr_t pointer);
 // typedef void  (APIENTRYP GPVIEWPORT)(GLint  x, GLint  y, GLsizei  width, GLsizei  height);
 //
+// static void  glowActiveTexture(GPACTIVETEXTURE fnptr, GLenum  texture) {
+//   (*fnptr)(texture);
+// }
 // static void  glowAttachShader(GPATTACHSHADER fnptr, GLuint  program, GLuint  shader) {
 //   (*fnptr)(program, shader);
 // }
@@ -353,6 +357,7 @@ import (
 )
 
 var (
+	gpActiveTexture               C.GPACTIVETEXTURE
 	gpAttachShader                C.GPATTACHSHADER
 	gpBindAttribLocation          C.GPBINDATTRIBLOCATION
 	gpBindBuffer                  C.GPBINDBUFFER
@@ -424,6 +429,10 @@ func boolToInt(b bool) int {
 	return 0
 }
 
+func ActiveTexture(texture uint32) {
+	C.glowActiveTexture(gpActiveTexture, (C.GLenum)(texture))
+}
+
 func AttachShader(program uint32, shader uint32) {
 	C.glowAttachShader(gpAttachShader, (C.GLuint)(program), (C.GLuint)(shader))
 }
@@ -675,6 +684,10 @@ func Viewport(x int32, y int32, width int32, height int32) {
 // InitWithProcAddrFunc intializes the package using the specified OpenGL
 // function pointer loading function. For more cases Init should be used
 func InitWithProcAddrFunc(getProcAddr func(name string) unsafe.Pointer) error {
+	gpActiveTexture = (C.GPACTIVETEXTURE)(getProcAddr("glActiveTexture"))
+	if gpActiveTexture == nil {
+		return errors.New("glActiveTexture")
+	}
 	gpAttachShader = (C.GPATTACHSHADER)(getProcAddr("glAttachShader"))
 	if gpAttachShader == nil {
 		return errors.New("glAttachShader")

internal/graphicsdriver/opengl/gl/package_windows.go

@@ -10,6 +10,7 @@ import (
 )
 
 var (
+	gpActiveTexture               uintptr
 	gpAttachShader                uintptr
 	gpBindAttribLocation          uintptr
 	gpBindBuffer                  uintptr
@@ -81,6 +82,10 @@ func boolToUintptr(b bool) uintptr {
 	return 0
 }
 
+func ActiveTexture(texture uint32) {
+	syscall.Syscall(gpActiveTexture, 1, uintptr(texture), 0, 0)
+}
+
 func AttachShader(program uint32, shader uint32) {
 	syscall.Syscall(gpAttachShader, 2, uintptr(program), uintptr(shader), 0)
 }
@@ -332,6 +337,10 @@ func Viewport(x int32, y int32, width int32, height int32) {
 // InitWithProcAddrFunc intializes the package using the specified OpenGL
 // function pointer loading function. For more cases Init should be used
 func InitWithProcAddrFunc(getProcAddr func(name string) uintptr) error {
+	gpActiveTexture = getProcAddr("glActiveTexture")
+	if gpActiveTexture == 0 {
+		return errors.New("glActiveTexture")
+	}
 	gpAttachShader = getProcAddr("glAttachShader")
 	if gpAttachShader == 0 {
 		return errors.New("glAttachShader")

internal/graphicsdriver/opengl/graphics.go

@@ -160,7 +160,7 @@ func (g *Graphics) Draw(indexLen int, indexOffset int, mode driver.CompositeMode
 		uniforms["scale"] = scale
 	}
 
-	uniforms["texture"] = source.textureNative
+	uniforms["texture/0"] = source.textureNative
 
 	if err := g.useProgram(program, uniforms); err != nil {
 		return err

internal/graphicsdriver/opengl/program.go

@@ -16,6 +16,8 @@ package opengl
 
 import (
 	"fmt"
+	"strconv"
+	"strings"
 
 	"github.com/hajimehoshi/ebiten/internal/driver"
 	"github.com/hajimehoshi/ebiten/internal/graphics"
@@ -132,8 +134,9 @@ type openGLState struct {
 	// programs is OpenGL's program for rendering a texture.
 	programs map[programKey]program
 
-	lastProgram  program
-	lastUniforms map[string]interface{}
+	lastProgram       program
+	lastUniforms      map[string]interface{}
+	lastActiveTexture int
 
 	source      *Image
 	destination *Image
@@ -251,6 +254,8 @@ func (g *Graphics) useProgram(program program, uniforms map[string]interface{})
 
 		g.state.lastProgram = program
 		g.state.lastUniforms = map[string]interface{}{}
+		g.state.lastActiveTexture = 0
+		g.context.activeTexture(0)
 	}
 
 	for key, u := range uniforms {
@@ -271,10 +276,19 @@ func (g *Graphics) useProgram(program program, uniforms map[string]interface{})
 			g.state.lastUniforms[key] = u
 		case textureNative:
 			// Apparently, a texture must be bound every time. The cache is not used here.
-			// TODO: Use another value than 0 when binding multiple textures.
-			g.context.uniformInt(program, key, 0)
-			// We don't have to call gl.ActiveTexture here: GL_TEXTURE0 is the default active texture
-			// See also: https://www.opengl.org/sdk/docs/man2/xhtml/glActiveTexture.xml
+			tokens := strings.SplitN(key, "/", 2)
+			if len(tokens) != 2 {
+				return fmt.Errorf("opengl: a uniform variable name for textures must be '[name]/[index]' but %s", key)
+			}
+			idx, err := strconv.Atoi(tokens[1])
+			if err != nil {
+				return fmt.Errorf("opengl: a uniform variable name for textures must be '[name]/[index]' but %s", key)
+			}
+			g.context.uniformInt(program, tokens[0], idx)
+			if g.state.lastActiveTexture != idx {
+				g.context.activeTexture(idx)
+				g.state.lastActiveTexture = idx
+			}
 			g.context.bindTexture(u)
 		}
 	}