fix marker scaling in freq display

uhabits-android/src/main/java/org/isoron/uhabits/activities/common/views/FrequencyChart.kt

@@ -29,6 +29,7 @@ import org.isoron.uhabits.core.utils.DateUtils.Companion.getShortWeekdayNames
 import org.isoron.uhabits.core.utils.DateUtils.Companion.getStartOfTodayCalendar
 import org.isoron.uhabits.core.utils.DateUtils.Companion.getStartOfTodayCalendarWithOffset
 import org.isoron.uhabits.core.utils.DateUtils.Companion.getWeekdaySequence
+import org.isoron.uhabits.core.utils.DateUtils.Companion.getWeekdaysInMonth
 import org.isoron.uhabits.utils.ColorUtils.mixColors
 import org.isoron.uhabits.utils.StyledResources
 import org.isoron.uhabits.utils.toSimpleDataFormat
@@ -166,6 +167,7 @@ class FrequencyChart : ScrollableChart {
 
     private fun drawColumn(canvas: Canvas, rect: RectF?, date: GregorianCalendar) {
         val values = frequency[Timestamp(date)]
+        val weekDaysInMonth = getWeekdaysInMonth(Timestamp(date))
         val rowHeight = rect!!.height() / 8.0f
         prevRect!!.set(rect)
         val localeWeekdayList: Array<Int> = getWeekdaySequence(firstWeekday)
@@ -174,7 +176,7 @@ class FrequencyChart : ScrollableChart {
             rect.offset(prevRect!!.left, prevRect!!.top + baseSize * j)
             val i = localeWeekdayList[j] % 7
             if (values != null)
-                drawMarker(canvas, rect, values[i])
+                drawMarker(canvas, rect, values[i], weekDaysInMonth[i])
             rect.offset(0f, rowHeight)
         }
         drawFooter(canvas, rect, date)
@@ -222,7 +224,7 @@ class FrequencyChart : ScrollableChart {
         canvas.drawLine(rGrid.left, rGrid.top, rGrid.right, rGrid.top, pGrid!!)
     }
 
-    private fun drawMarker(canvas: Canvas, rect: RectF?, value: Int?) {
+    private fun drawMarker(canvas: Canvas, rect: RectF?, value: Int?, frequency: Int) {
         // value can be negative when the entry is skipped
         val valueCopy = value?.let { max(0, it) }
 
@@ -230,7 +232,8 @@ class FrequencyChart : ScrollableChart {
         // maximal allowed mark radius
         val maxRadius = (rect.height() - 2 * padding) / 2.0f
         // the real mark radius is scaled down by a factor depending on the maximal frequency
-        val scale = 1.0f / maxFreq * valueCopy!!
+
+        val scale = 1.0f / frequency * valueCopy!!
         val radius = maxRadius * scale
         val colorIndex = min((colors.size - 1), ((colors.size - 1) * scale).roundToInt())
         pGraph!!.color = colors[colorIndex]

uhabits-core/src/jvmMain/java/org/isoron/uhabits/core/utils/DateUtils.kt

@@ -19,6 +19,7 @@
 package org.isoron.uhabits.core.utils
 
 import org.isoron.uhabits.core.models.Timestamp
+import java.time.YearMonth
 import java.util.Calendar
 import java.util.Calendar.DAY_OF_MONTH
 import java.util.Calendar.DAY_OF_WEEK
@@ -178,6 +179,26 @@ abstract class DateUtils {
             return getWeekdayNames(GregorianCalendar.SHORT, firstWeekday)
         }
 
+        /**
+         * Returns a vector of Int representing the frequency of each weekday in a given month.
+         *
+         * @param startOfMonth a Timestamp representing the beginning of the month.
+         */
+        @JvmStatic
+        fun getWeekdaysInMonth(startOfMonth: Timestamp): Array<Int> {
+            val month = startOfMonth.toCalendar()[Calendar.MONTH] + 1
+            val year = startOfMonth.toCalendar()[Calendar.YEAR]
+            val weekday = startOfMonth.weekday
+            val extraWeekdays = YearMonth.of(year, month).lengthOfMonth() - 28
+
+            val freq = Array(7) { 4 }
+            for (day in weekday until weekday + extraWeekdays) {
+                freq[day % 7] = 5
+            }
+
+            return freq
+        }
+
         @JvmStatic
         fun getToday(): Timestamp = Timestamp(getStartOfToday())