Very confused about scaling assets for multiple screens (density independence)

cocos2d-x C++
#1

Hi. I am trying to figure out how to stretch interface assets (buttons etc.) so that they consume the same amount of screen space on every Android device. I have read both the official Google guide “Supporting Multiple Screens” (http://developer.android.com/guide/practices/screens_support.html) and the Cocos2d-x guide, “Multi Resolution Support” (http://www.cocos2d-x.org/projects/cocos2d-x/wiki/Multi_resolution_support).

My issue is that it seems the method explained by Cocos2d-x does not take into consideration the screen density (DPI) or physical screen size of the device. So, an asset that appears large enough on a 1024x768 10" tablet will still seem very small on an Android phone that has a similar resolution but much higher DPI. I am trying to achieve the result as shown in Figure 3 on the Google guide.

Am I just not understanding the concept correctly or is it this difficult in Cocos2d-x? All of the multi resolution examples I’ve seen only consider iOS which is very simplistic by comparison to Android devices.

#2

I’m pretty sure what you are asking about is a scheduled feature for the next release.
http://www.cocos2d-x.org/issues/1939

#3

Kevin is right in my opinion because on Android you also have to provide different resources for different densities. A quick solution for you for know may be to make for example 4 directories like “ldpi”, “mdpi”, “hdpi”, “xhdpi” and put all other resources there, according to their target density/resolution. Then, when your app starts you can determine the device density (I think it can be done fairly easy on Java-side, I don’t know about passing a return value back from a JNI call though), and based on it determine the directory prefix for your resource access.

#4

Thanks for the information.

Then, when your app starts you can determine the device density (I think it can be done fairly easy on Java-side, I don’t know about passing a return value back from a JNI call though)

I discovered yesterday that there is already a method available in the latest release to get the DPI from within C++ (getDPI() within the CCDevice class). So, I’m able to use that as a multiplier to manually scale the desired assets based on DPI rather than screen resolution. However, now I’m going mad trying to position a scaled CCMenu (I apply the scale to the CCMenu object itself). If I have a properly positioned CCMenu at 1.0 scale, even scaling it to 1.1 causes the anchor to get out of whack and I can’t figure out exactly what’s happening…

#5

Can you expand a little more on getDPI? I have cocos2d-2.1beta3-x-2.1.1 and I can’t say that I see CCDevice in my project. Do I need to upgrade in order to use it?

#6

Kevin H wrote:

I’m pretty sure what you are asking about is a scheduled feature for the next release.
http://www.cocos2d-x.org/issues/1939

It looks like that issue was closed recently.

Does anyone have any documentation or samples showing how it should work?

#7

With 2.1.3, I used

float scale= CCDevice::getDPI()/160;