Reduced perfomance in new version

[moreginger]

Something about the new version seems to have reduced performance. I was getting 60fps with my fastgaussianblur shader, and now I'm getting ~35fps.

I think there is more buffer switching going on than used to happen, but I'm not sure that could explain it. Maybe it's applying the shader twice?

After inlining the shader code for the blur filter I got back up to 60fps, i.e. I did something like:

    local ps = love.graphics.getShader()
    local pc = love.graphics.setCanvas()
    local pbm = love.graphics.getBlendMode()

    love.graphics.setCanvas(c1)
    love.graphics.clear()
    _drawGameInternal(players, map, draw_map_end, shaders.cfg_all)

    love.graphics.setShader(shader)
    love.graphics.setBlendMode("alpha", "premultiplied")
    shader:send('direction', {1 / love.graphics.getWidth(), 0})
    love.graphics.setCanvas(c2)
    love.graphics.clear()
    love.graphics.draw(c1, 0, 0)
    shader:send('direction', {0, 1 / love.graphics.getHeight()})
    love.graphics.setCanvas(pc)
    love.graphics.draw(c2, 0, 0)

    love.graphics.setBlendMode(pbm)
    love.graphics.setShader(ps)

[vrld]

Strange. The draw of a chain with a fast gaussian blur should expand to this:

    local canvas = love.graphics.getCanvas()
    local shader = love.graphics.getShader()
    local color = {love.graphics.getColor()}

    love.graphics.setCanvas(front, back) -- a bug, at the moment
    love.graphics.clear()
    _drawGameInternal(...)

    local blendmode = love.graphics.getBlendMode()

    love.graphics.setColor(color)
    love.graphics.setBlendMode("alpha", "premultiplied")
   
    -- first pass
    shader:send('direction', {1 / love.graphics.getWidth(), 0})
    front, back = back, front
    love.graphics.setCanvas(front)
    love.graphics.clear()
    if shader ~= love.graphics.getShader() then
      love.graphics.setShader(shader)
    end
    love.graphics.draw(back)

    -- second pass
    shader:send('direction', {0, 1 / love.graphics.getHeight()})
    front, back = back, front
    love.graphics.setCanvas(front)
    love.graphics.clear()
    if shader ~= love.graphics.getShader() then
      love.graphics.setShader(shader)
    end
    love.graphics.draw(back)

    love.graphics.setShader()
    love.graphics.setCanvas(canvas)
    love.graphics.draw(front,0,0)

    love.graphics.setBlendMode(blendmode)
    love.graphics.setShader(shader)

So there is one more buffer switch than in your version. Unfortunately, the switch is needed to make chaining work.