Menu Building - Setting Navigation

The menu build section has 3 pages:

Our menu in demo2.mxp was saved with default navigation enabled. This is OK for a simple DVD that plays one title and stops, but we want to select the title from our root menu, so let's make a few changes.
The default navigation has both the First_Play PGC and Title Menu jump directly to the title. What we want is to jump to the root menu.
Click on the "Navigation" tab.

click on "FP"

click on "Pre Commands"

Now since we want to start with our root menu pull down the commands and select "Jump to PGC in System Space"

The destination is "Root Menu PGC".

The second drop-down will list all the titles. Since there is only one we have the correct title.
Now click "rpl" to replace the first command, a "Jump to Title" created by default navigation

Do the same for the title menu ("Unspecified_title" in Language Unit "Unspecified_0").

Now navigate to our root menu. Click + on VTS01, + on menu, + on Unspecified_1, then click on "Unspecified_root".
We want to remove the pre-command "jump to title" so our menu will run, click "Pre Commands" then click "Del"

We are going to process a button press by having each button, which is limited to one command, start the Post Commands and from there we will determine which button was pressed and what to do.
The button pressed is stored in SPRM8 multiplied by 1024. It is not possible to compare an SPRM to anything but a GPRM, and it is also not possible to compare a GPRM to a constant with a "Jump to Title" command. So there are 2 ways to determine the value of SPRM8 and jump. One way is to copy the SPRM into a GPRM and test directly, the other is set a GPRM to the value we are trying and compare it to the SPRM. Below is both methods for one button going to our single title.

		mov GPRM0, SPRM8			mov GPRM0, 1024
		If ( GPRM0 == 1024 ) GoTo title_1	if ( GPRM0 == SPRM8) JumpVTS_TT VTS01_TTL01
		Exit					Exit
title_1:	JumpVTS_TT VTS01_TTL01
The method on the right uses one less command, regardless of the number of titles, and uses no "GoTo" or labels, so we will use this method. We would use the other method if there more than one command is required for any button.
Start with setting GPRM0 to 1024

Now add a "Jump to Title", since this is conditional we need to check the "compare" box.

Set the compare boxes to make the jump if our GPRM (0 in this example) is equal to (==) SPRM8

Now the next command is not absolutely essential, and may be something else. It executes if none of the buttons we test for were pressed.

The last thing we need to do is have our title return to the menu when it is done. Navigate to the title PGC, click on "Post Commands"

And enter in a "Jump to PGC in System Space" to the root menu as we did for the pre commands of FP and the title menu.

At this point we have built demo3.mxp. Demo4 adds another title, and demo5 adds a third. On the next page we will add a "play all" title.
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