Add parameter useAlphaChannel to second IGUIEnvironment::addImage function as...

Add parameter useAlphaChannel to second IGUIEnvironment::addImage function as it's rather confusing when they have different defaults. Unfortunately can't use same parameter order anymore without messing up existing user-code now (some things can only be done right on first try...).

git-svn-id: svn://svn.code.sf.net/p/irrlicht/code/trunk@4223 dfc29bdd-3216-0410-991c-e03cc46cb475

include/IGUIEnvironment.h

@@ -300,11 +300,13 @@ public:
 	\param parent Parent gui element of the image.
 	\param id Id to identify the gui element.
 	\param text Title text of the image.
+	\param useAlphaChannel Sets if the image should use the alpha channel
+	of the texture to draw itself.
 	\return Pointer to the created image element. Returns 0 if an error
 	occurred. This pointer should not be dropped. See
 	IReferenceCounted::drop() for more information. */
 	virtual IGUIImage* addImage(const core::rect<s32>& rectangle,
-		IGUIElement* parent=0, s32 id=-1, const wchar_t* text=0) = 0;
+		IGUIElement* parent=0, s32 id=-1, const wchar_t* text=0, bool useAlphaChannel=true) = 0;
 
 	//! Adds a checkbox element.
 	/** \param checked Define the initial state of the check box.

source/Irrlicht/CGUIEnvironment.cpp

@@ -1113,7 +1113,7 @@ IGUIImage* CGUIEnvironment::addImage(video::ITexture* image, core::position2d<s3
 
 
 //! adds an image. The returned pointer must not be dropped.
-IGUIImage* CGUIEnvironment::addImage(const core::rect<s32>& rectangle, IGUIElement* parent, s32 id, const wchar_t* text)
+IGUIImage* CGUIEnvironment::addImage(const core::rect<s32>& rectangle, IGUIElement* parent, s32 id, const wchar_t* text, bool useAlphaChannel)
 {
 	IGUIImage* img = new CGUIImage(this, parent ? parent : this,
 		id, rectangle);
@@ -1121,6 +1121,9 @@ IGUIImage* CGUIEnvironment::addImage(const core::rect<s32>& rectangle, IGUIEleme
 	if (text)
 		img->setText(text);
 
+	if ( useAlphaChannel )
+		img->setUseAlphaChannel(true);
+
 	img->drop();
 	return img;
 }

source/Irrlicht/CGUIEnvironment.h

@@ -116,7 +116,7 @@ public:
 
 	//! adds an image. The returned pointer must not be dropped.
 	virtual IGUIImage* addImage(const core::rect<s32>& rectangle,
-		IGUIElement* parent=0, s32 id=-1, const wchar_t* text=0);
+		IGUIElement* parent=0, s32 id=-1, const wchar_t* text=0, bool useAlphaChannel=true);
 
 	//! adds a checkbox
 	virtual IGUICheckBox* addCheckBox(bool checked, const core::rect<s32>& rectangle, IGUIElement* parent=0, s32 id=-1, const wchar_t* text=0);