Add joystick support

[WetDesertRock]

Adds basic joystick support. Unfortunately the user has to track the
joysticks as the event callbacks give the joystick index. Currently I'm
mulling over the best way to do this.

If you don't want to merge yet tell me why and I'll make fixes. Because you are using SDL1 I don't have access to gamepad mapping APIs from SDL2.

[WetDesertRock]

Oh, for a usage example this is the program I use to test it out:

function juno.onLoad()
  joystick = nil
end

function juno.onUpdate(dt)
  if juno.joystick.getCount() >= 1 and joystick == nil then
    joystick = juno.joystick.open(0)
    print(string.format("Opening joystick with name '%s' reported id is %d",juno.joystick.getName(0),joystick:index()))
    print(string.format("  Axes count: %d",joystick:getAxisCount()))
    print(string.format("  Hat count: %d",joystick:getHatCount()))
    print(string.format("  Ball count: %d",joystick:getBallCount()))
    print(string.format("  Button count: %d",joystick:getButtonCount()))
  end
end

function juno.onJoyHatMotion(joystick,hat,state)
  print("Hat Motion:",joystick,hat)
  for d,v in pairs(state) do
    print("  ",d,v)
  end
end

[WetDesertRock]

Simplified it, you don't need to do any .open calls yourself. The only things you need will be in the juno.joystick.joysticks table array.

Here is a project to help test and visualize it.

function juno.onLoad()
  for _,joystick in ipairs(juno.joystick.joysticks) do
    print(string.format("Joystick with name '%s' reported id is %d",juno.joystick.getName(joystick:index()),joystick:index()))
    print(string.format("  Axes count: %d",joystick:getAxisCount()))
    print(string.format("  Hat count: %d",joystick:getHatCount()))
    print(string.format("  Ball count: %d",joystick:getBallCount()))
    print(string.format("  Button count: %d",joystick:getButtonCount()))
  end
  font_title = juno.Font.fromEmbedded(14)
  font_small = juno.Font.fromEmbedded(12)
  font_smallest = juno.Font.fromEmbedded(8)
end

local hatlines = {
  up = {6,0,6,4},
  down = {6,8,6,12},
  left = {0,6,4,6},
  right = {8,6,12,6}
}

function juno.onDraw()
  local y = 0
  for _,joystick in ipairs(juno.joystick.joysticks) do
    juno.graphics.setColor(1,1,1)
    juno.graphics.drawText(font_title,"Joystick: "..juno.joystick.getName(joystick:index()),20,y)
    y = y+17
    if joystick:getAxisCount() > 0 then
      local x = 20
      juno.graphics.drawText(font_small,"Axes: "..joystick:getAxisCount(), 20,y)
      y = y+15
      for i=0,joystick:getAxisCount()-1 do
        local xline = x+10 + (10*joystick:getAxis(i))
        juno.graphics.drawText(font_smallest,i,x,y)
        juno.graphics.drawLine(xline,y+8,xline,y+14)
        juno.graphics.drawLine(x,y+11,x+20,y+11)
        x = x+25
      end
      y = y+15
    end
    if joystick:getHatCount() > 0 then
      local x = 20
      juno.graphics.drawText(font_small,"Hats: "..joystick:getHatCount(), 20,y)
      y = y+15
      for i=0,joystick:getHatCount()-1 do
        juno.graphics.setColor(1,1,1)
        juno.graphics.drawText(font_smallest,i,x,y)
        for dir,enabled in pairs(joystick:getHat(i)) do
          local hl = hatlines[dir]
          if enabled then
            juno.graphics.setColor(1,1,1)
          else
            juno.graphics.setColor(0.5,0.5,0.5)
          end
          juno.graphics.drawLine(x+hl[1],y+hl[2]+5,x+hl[3],y+hl[4]+5)
        end
        x = x+16
      end
      y = y+16
    end
    juno.graphics.setColor(1,1,1)
    if joystick:getButtonCount() > 0 then
      local x = 20
      juno.graphics.drawText(font_small,"Buttons: "..joystick:getButtonCount(), 20,y)
      y = y+15
      for i=0,joystick:getButtonCount()-1 do
        juno.graphics.setColor(0,0,0)
        juno.graphics.drawText(font_smallest,i,x+6,y+6)
        if joystick:getButton(i) then
          juno.graphics.setColor(1,1,1)
        else
          juno.graphics.setColor(0.5,0.5,0.5)
        end

        juno.graphics.drawRect(x,y,12,12)
        x = x+16
      end
      y = y+16
    end
    juno.graphics.setColor(1,1,1)
  end
end