Cleanup: return gasmix by value

Currently, get_gasmix_from_event() and get_gasmix() return pointers
to either static or to (possibly changing) dive data. This seems like
a dangerous practice and the returned data should be used immediately.

Instead, return the gasmix by value. This is in preparation of
const-ifying input parameters of a number of core functions, which
will ultimately let the merge() function take const-arguments in
preparation of undo of dive-merging.

On common 64-bit systems gasmix (two "int"s) is the size of a pointer
and can be returned in a register.

On 32-bit systems a pointer to the struct to be filled out will be
passed.

Since get_gasmix() now returns a value, the first invocation is
tested by a NULL-initialized "struct event *". Document this in
a comment.

Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>

1 files changed, 3 insertions, 3 deletions

diff --git a/profile-widget/diveprofileitem.cpp b/profile-widget/diveprofileitem.cpp
index bedefb97e..94fb787b1 100644
--- a/profile-widget/diveprofileitem.cpp
+++ b/profile-widget/diveprofileitem.cpp
@@ -410,11 +410,11 @@ void DivePercentageItem::paint(QPainter *painter, const QStyleOptionGraphicsItem
 	for (int i = 1, modelDataCount = dataModel->rowCount(); i < modelDataCount; i++) {
 		if (i < poly.count()) {
 			double value = dataModel->index(i, vDataColumn).data().toDouble();
-			struct gasmix *gasmix = NULL;
+			struct gasmix gasmix = { 0 };
 			struct event *ev = NULL;
 			int sec = dataModel->index(i, DivePlotDataModel::TIME).data().toInt();
-			gasmix = get_gasmix(&displayed_dive, displayed_dc, sec, &ev, gasmix);
-			int inert = 1000 - get_o2(gasmix);
+			gasmix = get_gasmix(&displayed_dive, displayed_dc, sec, &ev, &gasmix);
+			int inert = 1000 - get_o2(&gasmix);
 			mypen.setBrush(QBrush(ColorScale(value, inert)));
 			painter->setPen(mypen);
 			painter->drawLine(poly[i - 1], poly[i]);