attempt a more fair container item squeezing

Ein Schrumpffreibetrag, faktisch schon Kommunismus ;-)

When short on space, items would be squeezed evenly, but this can turn
"a" and "a very long item with useless information text" into
"a very long item" and "", so in a pre-pass we check whether some very
large items cause the shortage and preferably squeeze them.

1 files changed, 29 insertions, 0 deletions

diff --git a/src/FbTk/Container.cc b/src/FbTk/Container.cc
index f7d5c35..0ddc421 100644
--- a/src/FbTk/Container.cc
+++ b/src/FbTk/Container.cc
@@ -386,6 +386,35 @@ void Container::repositionItems() {
             totalDemands += buttonDemands.back();
         }
         if (totalDemands) {
+            int overhead = totalDemands - total_width;
+            if (overhead > int(buttonDemands.size())) {
+                // try to be fair. If we're short on space and some items
+                // take > 150% of the average, we preferably shrink them, so
+                // "a" and "a very long item with useless information" won't
+                // become "a very long item with" and ""
+                overhead += buttonDemands.size(); // compensate forrounding errors
+                const int mean = totalDemands / buttonDemands.size();
+                const int thresh = 3 * mean / 2;
+                int greed = 0;
+                for (int i = 0; i < buttonDemands.size(); ++i) {
+                    if (buttonDemands.at(i) > thresh)
+                        greed += buttonDemands.at(i);
+                }
+                if (greed) {
+                    for (int i = 0; i < buttonDemands.size(); ++i) {
+                        if (buttonDemands.at(i) > thresh) {
+                            int d = buttonDemands.at(i)*overhead/greed;
+                            if (buttonDemands.at(i) - d > mean) {
+                                buttonDemands.at(i) -= d;
+                            } else { // do not shrink below mean or a huge item number would super-punish larger ones
+                                d = buttonDemands.at(i) - mean;
+                                buttonDemands.at(i) = mean;
+                            }
+                            totalDemands -= d;
+                        }
+                    }
+                }
+            }
             rounding_error = total_width;
             for (int i = 0; i < buttonDemands.size(); ++i) {
                 rounding_error -= buttonDemands.at(i)*total_width/totalDemands;