diff --git a/text_rendering/ren.c b/text_rendering/ren.c
index 8637b2c..1c3134d 100644
--- a/text_rendering/ren.c
+++ b/text_rendering/ren.c
@@ -58,7 +58,7 @@ const char * ren_err_msg[] = {
 };
 
 
-#define ELEM(x...) [x] = #x,
+#define ELEM(x) [x] = #x,
 const char *glerr[] = {
 	ELEM(GL_INVALID_ENUM)
 	ELEM(GL_INVALID_VALUE)
@@ -432,12 +432,21 @@ static int ren_draw_font_stack(void)
 		GL_FALSE,
 		sizeof(struct v_text),
 		(void*)sizeof(vec2_i)))
-	// TODO: implement size and damage tracking on stacks
-	GL(glBufferData(
-		GL_ARRAY_BUFFER,
-		ren.font_stack.idx*sizeof(struct v_text),
-		ren.font_stack.items,
-		GL_DYNAMIC_DRAW))
+	if (vtstack_changed(&ren.font_stack)) {
+		if (vtstack_size_changed(&ren.font_stack)) {
+			GL(glBufferData(
+				GL_ARRAY_BUFFER,
+				ren.font_stack.idx*sizeof(struct v_text),
+				ren.font_stack.items,
+				GL_DYNAMIC_DRAW))
+		} else {
+			GL(glBufferSubData(
+				GL_ARRAY_BUFFER,
+				0,
+				ren.font_stack.idx*sizeof(struct v_text),
+				ren.font_stack.items))
+		}
+	}
 	GL(glDrawArrays(GL_TRIANGLES, 0, ren.font_stack.idx))
 
 	GL(glDisableVertexAttribArray(REN_VERTEX_IDX))
@@ -478,12 +487,21 @@ static int ren_draw_box_stack(void)
 		GL_TRUE,
 		sizeof(struct v_col),
 		(void*)sizeof(vec2_i)))
-	// TODO: implement size and damage tracking on stacks
-	GL(glBufferData(
-		GL_ARRAY_BUFFER,
-		ren.box_stack.idx*sizeof(struct v_col),
-		ren.box_stack.items,
-		GL_DYNAMIC_DRAW))
+	if(vcstack_changed(&ren.box_stack)) {
+		if (vcstack_size_changed(&ren.box_stack)) {
+			GL(glBufferData(
+				GL_ARRAY_BUFFER,
+				ren.box_stack.idx*sizeof(struct v_col),
+				ren.box_stack.items,
+				GL_DYNAMIC_DRAW))
+		} else {
+			GL(glBufferSubData(
+				GL_ARRAY_BUFFER,
+				0,
+				ren.box_stack.idx*sizeof(struct v_col),
+				ren.box_stack.items))
+		}
+	}
 	GL(glDrawArrays(GL_TRIANGLES, 0, ren.box_stack.idx))
 
 	GL(glDisableVertexAttribArray(REN_VERTEX_IDX))
diff --git a/text_rendering/stack.h b/text_rendering/stack.h
index 63cfd25..816565c 100644
--- a/text_rendering/stack.h
+++ b/text_rendering/stack.h
@@ -3,17 +3,38 @@
 
 
 #define STACK_STEP 8
+#define STACK_SALT 0xbabb0cac
+
+// FIXME: find a way to not re-hash the whole stack when removing one item
+
+// incremental hash for every grow
+#define HASH(p, s, h)                                                          \
+{                                                                              \
+	unsigned char *v = (unsigned char *)(p);                               \
+	for (int x = (s); x; x--) {                                            \
+		(h) += v[x-1];                                                 \
+		(h) += (h) << 10;                                              \
+		(h) ^= (h) >> 6;                                               \
+	}                                                                      \
+	(h) += (h) << 3;                                                       \
+  	(h) ^= (h) >> 11;                                                      \
+  	(h) += (h) << 15;                                                      \
+}
 
 
 // TODO: add a rolling hash
 #define STACK_DECL(stackname, type)                                            \
 struct stackname {                                                             \
 	type *items;                                                           \
-	int size, idx;                                                         \
+	int size, idx, old_idx;                                                \
+	unsigned int hash, old_hash;                                           \
 };                                                                             \
 \
 \
-struct stackname stackname##_init(void) { return (struct stackname){0}; }      \
+struct stackname stackname##_init(void)                                        \
+{                                                                              \
+	return (struct stackname){0, .hash = STACK_SALT};                      \
+}                                                                              \
 \
 \
 int stackname##_grow(struct stackname *stack, int step)                        \
@@ -37,6 +58,7 @@ int stackname##_push(struct stackname *stack, type *e)                         \
 		if (stackname##_grow(stack, STACK_STEP))                       \
 			return -1;                                             \
 	stack->items[stack->idx++] = *e;                                       \
+	HASH(e, sizeof(type), stack->hash);                                    \
 	return 0;                                                              \
 }                                                                              \
 \
@@ -45,6 +67,8 @@ type stackname##_pop(struct stackname *stack)                                  \
 {                                                                              \
 	if (!stack || stack->idx == 0 || stack->size == 0)                     \
 		return (type){0};                                              \
+	stack->hash = STACK_SALT;                                              \
+	HASH(stack->items, sizeof(type)*(stack->idx-1), stack->hash);          \
 	return stack->items[stack->idx--];                                     \
 }                                                                              \
 \
@@ -53,11 +77,30 @@ int stackname##_clear(struct stackname *stack)                                 \
 {                                                                              \
 	if (!stack)                                                            \
 		return -1;                                                     \
+	stack->old_idx = stack->idx;                                           \
+	stack->old_hash = stack->hash;                                         \
+	stack->hash = STACK_SALT;                                              \
 	stack->idx = 0;                                                        \
 	return 0;                                                              \
 }                                                                              \
 \
 \
+int stackname##_changed(struct stackname *stack)                               \
+{                                                                              \
+	if (!stack)                                                            \
+		return -1;                                                     \
+	return stack->hash != stack->old_hash;                                 \
+}                                                                              \
+\
+\
+int stackname##_size_changed(struct stackname *stack)                          \
+{                                                                              \
+	if (!stack)                                                            \
+		return -1;                                                     \
+	return stack->size != stack->old_idx;                                  \
+}                                                                              \
+\
+\
 int stackname##_free(struct stackname *stack)                                  \
 {                                                                              \
 	if (stack) {                                                           \
@@ -68,5 +111,4 @@ int stackname##_free(struct stackname *stack)                                  \
 	return 0;                                                              \
 }                                                                              \
 
-
 #endif
diff --git a/ugui.c b/ugui.c
index 270e49a..7e09c0e 100644
--- a/ugui.c
+++ b/ugui.c
@@ -105,6 +105,7 @@ static ug_style_t style_cache = {0};
 }                                                                                   \
 
 
+// FIXME: is it really  necessary to clear (memset) the stack
 #define RESET_STACK(S)                                                         \
 {                                                                              \
 	memset(S.items, 0, S.idx*sizeof(*(S.items)));                          \