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Scripting Tutorial - Lesson 15: (Advanced) Using Mouse Controls withMultiple Classes

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In lesson 14 we saw how to use Keyboard controls to select and workwith multiple class objects. In this final lesson, we extend our mousecontrols in the same way. Most of what we need has already been putin place using the TrackedObject variable. All that is really needed is

to generalize the mouseDown function to work with out Objectstable rather than the specific case of the Square previously defined.

We need tostudy thevarious parts ofthemouseDownfunction closelyin order tounderstandwhat ishappening

here.

The functionbegins just astabKey did,with a loopthrough theobjects in theObjects table,allocating alocal variableobj to each inturn. As we

might expectfrom previousmouse work, ifthe mousedown occurswithin aparticularobject (usingthe containsfunction) thenthat becomesour selectedobject to be

Tracked.

As before, firstrelease it if theobject was

function on.mouseDown(x,y)

for i = #Objects, 1, -1 do

local obj = Objects[i]

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alreadyselected so weknow whatstate we are in.Then we defineTrackedObjectas obj, andindicate that itis selected.

The next two

lines define twonew globalvariables calledTrackOffsetxandTrackOffsety.You may havenoticed that ifwe click on anobjectsomewhereother than thecenter, the

object isinclined tojump to placethe centerunder themouse. TheseTrackedOffsetvalues serve toavoid this littlejump. Theyshould initiallybe defined aszero in our

on.resizefunction sothat they existwhen the pageis created andchanged.

Back totrackingmultipleobjects. Thetable.removeand table.insert

commandsserve to releaseany previousselected objectand replacewith thecurrent one -essentiallymoving it toprime positionin the table.This has theeffect desired -

the objectbeing clickedon becomesthe selected(Tracked)

if obj:contains(x, y) then

if TrackedObject ~= nil then

TrackedObject.selected= false

end

TrackedObject = obj

obj.selected = true

TrackOffsetx = TrackedObject.x- x

TrackOffsety = TrackedObject.y -y

table.remove(Objects, i)

table.insert(Objects, obj)

platform.window:invalidate()

break

end

end

end

function on.mouseUp(x,y)

if TrackedObject ~= nil then

TrackedObject.selected = false

end

TrackedObject = nil

end

function on.mouseMove(x,y)

if TrackedObject ~= nil then

TrackedObject.x = x + TrackOffsetx

TrackedObject.y = y + TrackOffsety

platform.window:invalidate()

end

end

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object and all iswell.

Only one otherchange is madeto mouseMoveand that issimply toinclude theTrackOffsetvalues referred

to previously.

Copy this codeintoscript_tut14.luaand you nowhave completedyour mission.Two objectsmay now beselected andcontrolled byeither mouse

or keyboard!

I would suggestthat you nowextend thisscript toinclude otherobjects. Simplydefine theseand then inserttheir definition

into the Objectstable and youwill be able tocontrol themjust as easily asyou control thesquare and thecircle. Multipleimages willwork just aswell.

Time then,

perhaps, to goback to theShape Patternsdocumentfeatured inlesson 11 andthink abouthow you maynow create yourown rich andpowerfuldocumentswhich work

equally wellwith bothhandheld andcomputer.

Click to see what such a document might look like

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Congratulationson completingthis series oflessons!

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