[Development] Changing qreal to a float

lars.knoll at nokia.com lars.knoll at nokia.com
Thu Feb 16 19:36:52 CET 2012

On 2/16/12 6:21 PM, "ext Girish Ramakrishnan" <girish at forwardbias.in>

>Hi Lars,
>On Thu, Feb 16, 2012 at 5:03 AM,  <lars.knoll at nokia.com> wrote:
>> On 2/16/12 12:16 PM, "ext Giuseppe D'Angelo" <dangelog at gmail.com> wrote:
>>>On 15 February 2012 22:56, Sean Harmer <sh at theharmers.co.uk> wrote:
>>>> On 15/02/2012 11:53, andre.poenitz at nokia.com wrote:
>>>>> Anyway. It's probably better to go for any kind of uniformity. If
>>>>>that's single precision, it should be made clear  that
>>>>>are not meant for applications needing "polygons" in general. Maybe
>>>>>should consider adding some QPolygonD/QRectD/... later to get the
>>>>>functionality back. Until these exist, it might be worthwhile to keep
>>>>>the (then unconditional) typedef though, to allow easy creation of
>>>>>custom builds of Qt with double precision coordinates.
>>>> Why not make these classes into templates and have typedefs for the
>>>> float and double cases? It always confused me why QVector<n>D mixed
>>>> qreals and floats.
>>>I agree, although typedefs will unfortunately break all forward
>> That would break quite a bit of code, so I'm against it.
>> It's not a big deal to simply add the QRectD, etc. types if required.
>> In any case, here's the patch to close the issue:
>> http://codereview.qt-project.org/16551
>I thought we were agreeing upon deprecating qreal (i.e leave it as-is)
>and use float and double explicitly inside Qt. At least, that's what I
>+1d for :) The patch above changes qreal and doesn't deprecate it.

We need to do this in steps. Right now, this would break signal/slot
connections wherever a real type is being used (because of the string
based matching). Kent is working on improvements to the metaobject system
(see http://codereview.qt-project.org/#change,14763). Once that is in I
can do the s/qreal/float/ in all of Qt without breaking connections that
still use qreal for arguments because the new format stores the actual
type and not the string.

But the patch above ensures we have the right binary format for qreal's,
and changing over to use float in the method signature is binary
compatible (once we don't match on strings in connect() anymore).


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