Monday, September 3, 2012
Petit Computer Journal #5
Petit Computer Journal #5 - Buttons and Touchscreen
Let's take a little detour for now. We should be doing strings and graphics, but I want to do something else real quick: Buttons, Touchscreen, and Keyboard. In other words: INPUT.
We have done buttons, touchscreen, and keyboard inputs before. However, I'm interested in doing them all at once. And the trick is to do it without stopping the other input methods. That's not too easy.
Regarding keyboard input method that doesn't stop other process, we have INKEY$. We also have touchscreen variables TCHX,TCHY and all those. How about buttons? We have BUTTON(0), and that is sufficient. So, at the surface, we have all that we need.
The thing is, I don't want to have to structure the program into multi-threading format at this point in time. So, we will have to make some sacrifices. The INKEY$ is well enough. How about buttons and touchscreen?
In Touchscreen, it is convenient to have a drag-and-drop process. That means X1,Y1,X2,Y2,TouchStatus. Let's build that capability.
IF TCHST==0 THEN TS1=TCHST:RETURN
IF TS1==0 THEN TX1=TCHX:TY1=TCHY:TS1=1
IF TS1==1 THEN TX2=TCHX:TY2=TCHY
That looks simple enough. Basically, we want to update the variables if TCHST==1. The first line takes care of that by returning from subroutine if TCHST==0. Next, we want to see which pair we want to update X1,Y1 or X2,Y2? And that's all there is to it!
The buttons isn't so simple, though. There are 4 possible arrangements that I can see:
1. No Wait+Multiple: BUTTON(0)
2. No wait+Single: @SETB1
3. Wait+Multiple: @SETB2
4. Wait+Single: @SETB3
Of these, we want no wait version. If the no wait version is equivalent to INKEY$, then the wait version is equivalent to INPUT. The whole process involve trying out different versions of the commands. You see the finished product as clean, but I assure you that the process involves repeatedly trying and failing to come up with that clean method. You do not see the hard work that is done. At least, if you ever wonder why my progress is at glacial pace, you know the reason: Lacking tutorial such as this, I do a lot of experiments, not all of them successful.
There are 4 cases and only 3 subroutines. The first case can be easily met via BUTTON(0). The rest is done with simple subroutines. It only works on the first 8 bits, corresponding to UDLRABXY. This is because the method I use requires string characters, and those only goes to 255. I typed in the character in the actual program, but for the purpose of tutorial there are two index variables used by INSTR()
I use this technique a lot as it simplifies things greatly. It's not the fastest running code, and so only amateur hobbyist would use it. Certainly not a professional quality code. If need be, I may changed the code later to a more efficient one. But I like doing rapid prototyping in the beginning.
One more thing, the no wait version is tricky. If you check out the clock, you will see that no-wait @SETB1 does cause the program to stop when you press the button for a long time. A way to fix this would be to use a variable, but I would rather just do it directly with BUTTON(0) or @SETB2.
@SETB1 :'SINGLE FIRE
INBUTTON$="":Z=BUTTON(0):IF!Z THEN RETURN
FOR Z=0 TO 1:Z=BUTTON(3):NEXT:Z=Z AND 255
Z=INSTR(IST2$,CHR$(Z)):IF Z< 0 THEN RETURN
INBUTTON$="":Z=BUTTON(0):IF!Z THEN RETURN
Z=Z AND 255:Z=INSTR(IST1$,CHR$(Z)):IF Z< 0 THEN RETURN
FOR Z=0 TO 1:VSYNC 1:Z=BUTTON(1):NEXT:Z=Z AND 255
Z=INSTR(IST2$,CHR$(Z)):IF Z< 0 THEN RETURN
And those are the functions. Next, let's write a quick demo program to demonstrate the different functions. It may be best that you write a program and save it because you will be using this at all times. I know I do!
'BUTTON/TOUCHSCREEN TEST EXAMPLE
IF INBUTTON$!="" OR TS1 THEN GOSUB @DT
@DT :'DRAW TEXT
IF INBUTTON$!="" THEN L1=(L1+1)%32:LOCATE L1,1:?INBUTTON$;
IF INBUTTON$=="L" THEN P1=P1+15
IF INBUTTON$=="R" THEN P1=P1+1
IF INBUTTON$=="U" THEN P2=P2+15
IF INBUTTON$=="D" THEN P2=P2+1
FOR X=SX1 TO SX2:FOR Y=SY1 TO SY2:
C$=CHR$(151):COLOR P2:'0=BIG BLOCK CHARACTER IN PETIT COMPUTER
IF X==SX1 OR X==SX2 THEN C$=CHR$(150):COLOR P1:'1=VERT LINE
IF Y==SY1 OR Y==SY2 THEN C$=CHR$(149):COLOR P1:'2=HORZ LINE
IF X==SX1 AND Y==SY1 THEN C$=CHR$(152):COLOR P1:'3=UPPERLEFT
IF X==SX2 AND Y==SY1 THEN C$=CHR$(153):COLOR P1:'4=UPPERRIGHT
IF X==SX1 AND Y==SY2 THEN C$=CHR$(154):COLOR P1:'5=LOWERLEFT
IF X==SX2 AND Y==SY2 THEN C$=CHR$(155):COLOR P1:'6=UPPERRIGHT
For some reason, my computer does not read my memory card. That's a setback. I have to have those special characters, and so, I'm forced to do it the hard way, which is very annoying. However, either I overcome that setback, or I don't do this at all. I can work on the DSi no problem, but if I want to share it, I have to do this thankless work of translating those characters into their numeric equivalent. I wrote a simple program just for that:
FOR I=S TO S+15
LOCATE 0,R:?I;:LOCATE 5,R:?CHR$(I)
IF INBUTTON$=="U" THEN S=S+16
IF INBUTTON$=="D" THEN S=S+256-16
?:?"S=";S;" ";INBUTTON$:WAIT 60:'OPTIONAL FOR DEBUGGING
And that's it. Not even 10 minutes. You need to provide Subroutine @SETB3, but that's trivial. Just copy the one above.
Problems and How to Ask Questions
You know how people say there's no such thing as stupid questions? I know I'm bucking the convention here, but I'd say there are! Here's a sample, quoted in its entirety:
"Help! SAVE doesn't work."
I'm not saying that SAVE command is so easy that it cannot fail. I am saying that the question doesn't even begin to show the framework in which the problem occurs. We need more data! You know how PRINT statement works, right? What if there's somebody who ask help like this: "How do you use PRINT?", following your answer with "It doesn't work."
You know it works, and you know how it works. The problem is, how does it doesn't work? You have no clue as to what problem this person encounter. So, here is how you handle a problem that you cannot solve, because the unwritten rule is, if you ask a question that you later answer without any prompting whatsoever, YOU JUST ASKED A STUPID QUESTION THAT YOU KNOW THE ANSWER TO!
Problem solving technique:
1. Ran into problem, WRITE IT DOWN!
2. Write down all the relevant elements.
3. Read the Manual/Help file
4. WRITE ALL THE POTENTIAL SOLUTIONS DOWN.
5. Implement them all.
That's step-by-step. You are not allowed to skip steps. Half of your problems can be solved this way. As for the rest, well, that's when it gets tricky.
Hard Problem Solving:
1. You are tired. STOP AND GO TO SLEEP!
2. Wake up. Eat something solid
3. Repeat problem solving steps above.
By this time, if you followed this advice, a lot of you would do a lot of face palming "Of course! Why didn't I think of that?" sequence. That happens to me, too.
Stubborn Problem Solving:
1. You are sadly misunderstanding the problem. YOU are at fault!
2. Find 3 different interpretations to the problem.
3. Also, find 3 different OTHER places where it may cause the problem.
4. Consult the manual for help.
It may help to pretend that you're a newbie who doesn't understand everything. Don't laugh. It works! I used that technique myself occasionally. For the next level you must first admit that you are stupid. No, really. You are! You may humbly ask other people for help. Ever seen somebody arrogantly ask for solution to their problem? That never gets resolved, does it? Bingo.
Impossible Problem Solving:
1. Explain What the Problem is
2. Tell what you think are the relevant elements
3. Show what you did to solve the problem
4. WRITE THE SIMPLEST, SHORTEST CODE to explain the problem.
That last element is vital. No one wants to read 200 lines of code just to debug your program. So, there. Problem solving explained. Either that or you explain your problem to a duck.
Haha, joking aside, the ability to properly explain your problem is crucial in getting it solved. You don't want to ask a question like a grade schooler if you can ask your questions like a professor!
My PRINT doesn't work!
1. Did you type it in RUN(direct) mode or EDIT (deferred) mode?
2. Did it give you Syntax Error?
3. Did it print 0?
4. Did you set VISIBILITY?
What if PRINT doesn't work because it was set to XOR Mode? How will you respond to that? You can't set Console to XOR mode, right? How does that work? This is where giving out sample code is crucial.
COLOR SET XOR ! DOIT
PRINT "HELLO WORLD"
SET and DOIT ARE not keywordS. Why is there an exclamation mark preceding it? Because when I put it after the word (DOIT!), the computer complained, DUH!
You see how sample source code clarifies the issue quickly and easily? Don't act like a grade schooler. Ask questions like a professor! When I see the words "I don't understand ..." it'd better be followed by "These are the things I tried in order to understand it."