From 49229c75f3a85b72a7073a68a5a6fe38218b6357 Mon Sep 17 00:00:00 2001
From: Daniel Barlow <dan@telent.net>
Date: Sat, 21 May 2022 20:30:54 +0100
Subject: [PATCH] add per-view transformation matrices

Note that this breaks output layout. Would prefer to deal with that
stuff ("monitor 1 is left of monitor 2") in Lua for more flexibility
---
 kiwmi/include/desktop/view.h  |  1 +
 kiwmi/kiwmi/desktop/output.c  | 33 +++++++++++++++----------
 kiwmi/kiwmi/desktop/view.c    |  5 ++++
 kiwmi/kiwmi/luak/kiwmi_view.c | 45 +++++++++++++++++++++++++++++++++++
 4 files changed, 71 insertions(+), 13 deletions(-)

diff --git a/kiwmi/include/desktop/view.h b/kiwmi/include/desktop/view.h
index 3055304..90a4ad6 100644
--- a/kiwmi/include/desktop/view.h
+++ b/kiwmi/include/desktop/view.h
@@ -54,6 +54,7 @@ struct kiwmi_view {
 
     int x;
     int y;
+    float matrix[9];
 
     bool mapped;
     bool hidden;
diff --git a/kiwmi/kiwmi/desktop/output.c b/kiwmi/kiwmi/desktop/output.c
index 2f2564a..9b2bcac 100644
--- a/kiwmi/kiwmi/desktop/output.c
+++ b/kiwmi/kiwmi/desktop/output.c
@@ -101,29 +101,36 @@ render_surface(struct wlr_surface *surface, int sx, int sy, void *data)
     struct kiwmi_render_data *rdata = data;
     struct kiwmi_view *view         = rdata->data;
     struct wlr_output *wlr_output   = rdata->output;
+    float mat[9] = { 1,0,0, 0,1,0, 0,0,1 };
 
     struct wlr_texture *texture = wlr_surface_get_texture(surface);
     if (!texture) {
         return;
     }
 
-    int ox = rdata->output_lx + sx + view->x - view->geom.x;
-    int oy = rdata->output_ly + sy + view->y - view->geom.y;
+    wlr_matrix_translate(mat,
+			 sx + view->x - view->geom.x,
+			 sy + view->y - view->geom.y);
+    wlr_matrix_scale(mat, surface->current.width, surface->current.height);
+    wlr_matrix_multiply(mat, view->matrix, mat);
 
-    struct wlr_box box = {
-        .x      = ox * wlr_output->scale,
-        .y      = oy * wlr_output->scale,
-        .width  = surface->current.width * wlr_output->scale,
-        .height = surface->current.height * wlr_output->scale,
-    };
-
-    float matrix[9];
     enum wl_output_transform transform =
         wlr_output_transform_invert(surface->current.transform);
-    wlr_matrix_project_box(
-        matrix, &box, transform, 0, wlr_output->transform_matrix);
 
-    wlr_render_texture_with_matrix(rdata->renderer, texture, matrix, 1);
+    if (transform != WL_OUTPUT_TRANSFORM_NORMAL) {
+	wlr_matrix_translate(mat, 0.5, 0.5);
+	wlr_matrix_transform(mat, transform);
+	wlr_matrix_translate(mat, -0.5, -0.5);
+    }
+
+    /* looking at the definition of wlr_matrix_project_box,
+     * wlr_output->transform_matrix would be
+     * better named wlr_output->projection_matrix
+     */
+
+    wlr_matrix_multiply(mat, wlr_output->transform_matrix, mat);
+
+    wlr_render_texture_with_matrix(rdata->renderer, texture, mat, 1);
 
     wlr_surface_send_frame_done(surface, rdata->when);
 }
diff --git a/kiwmi/kiwmi/desktop/view.c b/kiwmi/kiwmi/desktop/view.c
index c741d8d..6fa6f46 100644
--- a/kiwmi/kiwmi/desktop/view.c
+++ b/kiwmi/kiwmi/desktop/view.c
@@ -293,6 +293,11 @@ view_create(
 
     view->x = 0;
     view->y = 0;
+    for(int r=0; r < 3; r++) {
+	for(int c=0; c < 3; c++) {
+	    view->matrix[r*3+c] = (r == c) ? 1 : 0;
+	}
+    }
 
     wl_list_init(&view->children);
 
diff --git a/kiwmi/kiwmi/luak/kiwmi_view.c b/kiwmi/kiwmi/luak/kiwmi_view.c
index 791347b..f856665 100644
--- a/kiwmi/kiwmi/luak/kiwmi_view.c
+++ b/kiwmi/kiwmi/luak/kiwmi_view.c
@@ -247,6 +247,49 @@ l_kiwmi_view_move(lua_State *L)
     return 0;
 }
 
+static int
+l_kiwmi_view_matrix(lua_State *L)
+{
+    struct kiwmi_object *obj =
+        *(struct kiwmi_object **)luaL_checkudata(L, 1, "kiwmi_view");
+
+    if (!obj->valid) {
+        return luaL_error(L, "kiwmi_view no longer valid");
+    }
+
+    struct kiwmi_view *view = obj->object;
+
+    lua_newtable(L);
+    for(int i=0; i< 9; i++) {
+	lua_pushnumber(L, view->matrix[i]);
+	lua_seti(L, -2, 1 + i);
+    }
+
+    return 1;
+}
+
+static int
+l_kiwmi_view_set_matrix(lua_State *L)
+{
+    struct kiwmi_object *obj =
+        *(struct kiwmi_object **)luaL_checkudata(L, 1, "kiwmi_view");
+
+    if (!obj->valid) {
+        return luaL_error(L, "kiwmi_view no longer valid");
+    }
+
+    struct kiwmi_view *view = obj->object;
+
+    luaL_checktype(L, 2, LUA_TTABLE);
+
+    for(int i=0; i< 9; i++) {
+	lua_geti(L, 2, 1 + i);
+	view->matrix[i] = lua_tonumber(L, -1);
+    }
+
+    return 0;
+}
+
 static int
 l_kiwmi_view_pid(lua_State *L)
 {
@@ -434,6 +477,8 @@ static const luaL_Reg kiwmi_view_methods[] = {
     {"imove", l_kiwmi_view_imove},
     {"iresize", l_kiwmi_view_iresize},
     {"move", l_kiwmi_view_move},
+    {"matrix", l_kiwmi_view_matrix},
+    {"set_matrix", l_kiwmi_view_set_matrix},
     {"on", luaK_callback_register_dispatch},
     {"pid", l_kiwmi_view_pid},
     {"pos", l_kiwmi_view_pos},